READ: Theresa May's full speech in Scotland on the Union

In the speech, May claims that while other parties "can be relied on" to make devolution a success "an SNP Scottish Government will only ever seek to further the agenda of separation".

May said it meant the UK Government had an obligation to "realise the full benefits of the Union".

READ MORE: First Minister tells May her legacy will be 'Scottish independence'

You can read her full speech, delivered on what is her last trip to Scotland as Prime Minister, below.

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Twenty years on from the creation of a new devolved Parliament for Scotland and devolved assemblies for Wales and Northern Ireland… …institutions which have strengthened our democracy and enriched our public life… …the question of how we can secure our Union for the future is being asked with ever more urgency.

It is not hard to see why.

Here in Scotland, the independence referendum in 2014, followed in quick succession by the SNP’s success in the general election a year later, sent political shockwaves across the United Kingdom.

In Northern Ireland, after the longest sustained period of devolved government since the 1970s, the power-sharing institutions set up under the Belfast/Good Friday Agreement and its successors have now sadly not functioned for over two years.

In Wales, the party which campaigns for Welsh separation from the United Kingdom this year scored its best result in a national election this century.

And the leader of the party that topped the poll in those elections in England speaks casually of the potential break-up of our Union.

All of this against the backdrop of Brexit – a profound constitutional change that is putting political and administrative strains on the Union.

When Gordon Brown recently said that he fears the Union is ‘more imperilled now than it has ever been’ he voiced the fears of many.

I care passionately about our Union. I certainly do not underestimate the scale of the challenge it faces. But I am optimistic about its future.

The Union has proved a remarkably durable and flexible relationship over the centuries – evolving to meet the needs and aspirations of the peoples of these islands.

Its strengths are substantial.

The benefits it brings to each of its constituent parts significant.

And I believe if those of us who care for it act wisely, if we draw on its great strengths and think creatively about how to build on them in the years ahead, its future can and will be a bright and prosperous one.

Now the first step is to appreciate the historical complexity and intricacy of our United Kingdom.

When we talk about ‘the Union’ we mean the modern, 21st century relationship that exists today between the historic nations of Great Britain – England, Wales and Scotland – and Northern Ireland.

But ‘the Union’ is not the result of a single event.

It has evolved over many centuries.

Legal union between England and Wales was implemented by the Tudors – a royal house with Welsh roots.

England and Wales were united in personal union with Scotland in 1603 by a Scottish royal house, the Stuarts.

Political Union was achieved under the last Stuart monarch, Queen Anne, with the creation of the Kingdom of Great Britain.

A century later, another Act of Union created the United Kingdom of Great Britain and Ireland.

And following the creation of Northern Ireland in 1921, the United Kingdom took on the form we know today.

It is clear from that potted history that when we talk about ‘the Union’ we are in fact talking about a complex network of connections stretching back over the centuries.

The economic architecture of the Union has been remarkably stable and a huge source of strength.

So much so that we can sometimes take it for granted.

We can forget that the UK’s Customs Union created the first modern industrial marketplace.

That the pound sterling has served the four nations of the Union for centuries.

And that our fully integrated internal market – with no barriers to doing business – remains the most important market for businesses across the UK.

It is sometimes said that to celebrate these economic benefits of the Union while at the same time arguing that we should deliver Brexit is contradictory.

But that is to mistake the nature of the United Kingdom.

Because historical milestones and economic hardwiring are important – but they are not the true essence of our Union.

It is not just a constitutional artefact, not just a marketplace for goods.

It is a family of nations and a union of people. And the evidence of that social union is all around us.

As Prime Minister, I have seen it first-hand.

In our armed forces, where national and local identities are celebrated, but where every soldier, sailor, airman and marine shares a common loyalty.

In our diplomats, drawn from every corner of the UK, representing our shared liberal values of democracy and the rule of law internationally.

You see it in the good that UK Aid does, helping the poorest people around the world, much of it directed from the DFID HQ in East Kilbride.

In our Security Services, amongst the world’s best, working every day to keep everyone in the UK safe.

All of these public servants come together from different backgrounds to serve a common purpose – achieving more as one Team UK than they ever could separately.

You see that social Union in our shared institutions – the glue that holds our Union together.

The BBC, providing bespoke services in every part of the UK, broadcasting in the different languages of the UK nations, but also sustaining a common, UK-wide conversation.

The NHS, whose core principles of high quality healthcare, free at the point of use, according to clinical need, are the definition of our solidarity as a union of people.

These are the institutional examples of the diversity and harmony of our Union.

But the most tangible demonstrations of that Union of people are the personal stories being written every day within families and friendships across the country.

At every level, there is an alchemy inherent in our Union – the achievement of something greater because our four nations worked together.

It can sometimes be hard to articulate the core tenets that underwrite that success – to transcend specific examples and get to the coherence of the whole.

Today I want to identify three core strengths which for me define our Union – and which will be its surest safeguards in the years ahead.

Its reliance on the support of its people; its respect for different identities; and the pooling and sharing of risks and rewards.

First, our Union rests on and is defined by the support of its people.

It is not held together by a rigid constitution or by trying to stifle criticisms of it.

It will endure as long as people want it to – for as long as it enjoys the popular support of the people of Scotland and Wales, England and Northern Ireland.

We showed that in 2014.

The UK and Scottish Governments came together to agree the terms of a referendum on independence.

Both sides committed to respect the result.

The then First Minister and his then deputy both asserted that it was a ‘once in a generation’ or ‘once in a lifetime’ event.

And if a majority had supported independence, the UK Government would have accepted that result – no question.

But the people of Scotland did not vote for independence.

A clear and decisive majority of ten percentage points gave the Union their backing and their decision should be respected.

So when Nicola Sturgeon requested of the UK Government in 2017 the power to legislate for a second independence referendum, just three years after that historic vote, I had no hesitation in firmly saying ‘no’.

In the future, it will be for others to decide based on the prevailing circumstances how to respond to separatism.

But the principle is clear – the Union can and will only prosper if it enjoys the support of its people.

The second core strength is the respect we give within our Union for different identities.

Being together in a Union does not mean we lose our local and national identities.

We can support a football team representing one of the UK nations, and cheer on Team GB at the Olympics and feel that there is nothing incoherent about it.

Our nationalities, along with our religions, our racial heritages, our sexualities and many other factors are part of the tapestry of each individual.

You can be Welsh and Muslim and British.

You can be Glaswegian and gay and British.

You might feel more English than British. Or vice versa.

You do not have to choose. You can be both, or either, or neither.

The Union has never been about uniformity.

Scotland, as a proud and historic nation, retained its separate legal, religious and educational systems within the Union.

The Belfast Agreement guarantees the ‘birth right of all the people of Northern Ireland to identify themselves and be accepted as Irish or British, or both, as they may so choose.’ The Welsh language enjoys an equal legal status with English – fel y dylai fod “as it should be”.

Diversity is part of the deal.

That respect for multiple identities also includes respect for those who do not identify as British.

It is legitimate in a democracy for anyone to seek to change the constitutional settlement through legal means.

Ours is a Union that seeks to work for everyone – where everyone committed to democracy and the rule of law can feel at home and part of the whole.

But we must also nurture the things that bring us together – and celebrate the shared bonds and interests that unite us.

This accommodation of multiple, layered identities within a common system of values is one of the UK’s greatest assets.

It is a hallmark of what it is to be British and it is a defining strength of our Union.

The third core strength is about how we interact as a Union of people.

That we face challenges together and freely pool the resources at our disposal in order to overcome them.

We see that most clearly and movingly in the darkest times.

This year I had the honour to represent the United Kingdom at the D-Day commemorations.

What better example of success achieved by pooling our national resources to overcome a shared risk could you find?

It was a success born of shared sacrifice which ensured our very survival – and the survival of freedom and democracy for the whole world.

And it was only possible because we were a United Kingdom of four nations but one people.

But it is not just in times of war that we see that principle in action.

The broad shoulders of the world’s fifth-largest economy allowed the whole of the UK to weather the storm of the global financial crisis a decade ago.

Banks headquartered in Edinburgh and London were rescued by the Treasury – action that was only possible because of the size and strength of the whole UK economy.

The UK Government has been able to take unprecedented action to support the oil and gas sector following the decline in the international oil price – with public spending here in Scotland protected, even as North Sea tax receipts dwindled.

The UK and Welsh Governments worked in partnership to support the steel sector, ensuring the sustainability of steel production in South Wales, and keeping the iconic blast furnaces at Port Talbot open.

And it is not just about the benefits that the Union gives to its parts, but about what those parts contribute to the whole.

The great Scottish universities – some of the best in the world – which help make the UK an education powerhouse.

The engineering innovation in Cardiff, where the world’s first compound semiconductor cluster is pioneering a crucial technology of the future.

Northern Ireland’s emerging status as the world’s biggest and most beautiful TV studio – renowned for the highest quality programming, from ‘Line of Duty’ to ‘Game of Thrones.’ These are some of the brightest jewels in the United Kingdom’s crown.

Every business, every community, every family in each nation of the UK is part of that bigger whole and makes their contribution to it.

Time and again the benefits of sharing challenges and opportunities together and pooling our resources to meet them are clear.

It is baked into how our Union is governed.

The Barnett formula delivers spending per head significantly higher in Northern Ireland, Scotland and Wales than the UK average, to reflect particular needs.

At its heart is the principle of solidarity – that we are one people. That we have a common stake in each other’s success.

That the happiness of someone in Belfast is the care and concern of someone in Bolton or Brecon or Bridge of Allan.

These core strengths provide an emotional and intellectual framework through which to understand the benefits our Union brings to all its people.

They are noble principles that define us and which we can take pride in.

And as we look to the future, and the questions it will ask of us, we can take confidence that our Union is built on rock-solid foundations.

Safeguarding our Union for the long-term will take work.

Right now, it means doing two things urgently.

First, delivering a Brexit that works for the whole United Kingdom – for its individual parts and for the whole.

And second, being much more creative and energetic in strengthening the ties that bind us and reinforcing the glue that holds our Union together.

On Brexit, the challenge is serious.

Majorities of voters in England and Wales voted to leave, while majorities in Scotland and Northern Ireland voted to remain.

That fact places an important responsibility on a Unionist government committed to delivering on the referendum result.

Ensuring that we leave the EU in a way that protects the interests of all parts of the UK has been one of my central priorities over the last three years – and I regret that I will soon be stepping down with that ambition as yet unfulfilled.

Leaving with a good deal, one that works for the whole UK, is the very best possible outcome and the right one to be working towards.

It means we can get on and build a good new relationship with our European friends and partners.

And it is far better than leaving without a deal – which would have undoubted consequences for our economy and for the Union.

Clearly a major barrier to my success in getting a deal agreed was the challenge posed by the UK’s land border with another EU member state.

A border which weaves its way through farms and villages, bisects hundreds of roads and lanes, and which is crossed and re-crossed by thousands of people every day.

And a border which is bound up with the complexities of an often troubled past.

At the heart of the Belfast Agreement, which enabled the people of Northern Ireland to move beyond that past into a shared future, was a compromise.

That people who identify as Irish can live in Northern Ireland but, to all intents and purposes, operate across the whole of Ireland in their day to day lives and in their business activities without any semblance of a border.

That compromise was enabled by having a seamless border.

The backstop insurance policy we agreed with the EU, which would have been activated only if we were unable to agree our new relationship within the implementation period, respected that compromise.

And the future relationship will need to respect it.

It will be for my successor to resolve that issue and I will not today seek to provide any advice on the matter.

I will simply say this.

There can and must be no false choice between honouring the solemn commitments of the Belfast Agreement and delivering on the decision of the British people in the EU referendum.

We must do both.

Brexit certainly poses a challenge for the Union – but it is one which can be met by working with the grain of the United Kingdom’s core strengths.

And in forcing us politicians to pay more attention to the dynamics of our Union, it is a challenge we can and should use as the opportunity to strengthen that Union for the long term.

The need to do so long pre-dates Brexit.

One of the lessons of the independence referendum in 2014 was that those of us who believe in our United Kingdom need to do much more to make and demonstrate the emotional case for it – and to strengthen the ties that bind it together.

As we do so, we can take confidence in our Union’s adaptability. And there is no better example of that adaptability than devolution.

Twenty years since the creation of the Scottish Parliament, the National Assembly for Wales and the Northern Ireland Assembly it is clear that devolution is a source of strength for the UK – not a sign of its weakness.

It is the form of government best suited to our geography, our history and our future.

Stormont, Holyrood and Cardiff Bay are democratic expressions of the multiple identities that define the Union.

And devolved legislatures working alongside a United Kingdom Parliament elected by every citizen of the Union, containing representatives of every community in the Union, means the best of both worlds.

The benefit of more responsive and representative government for Scotland, Wales and Northern Ireland, without sacrificing the strength and security that pooling and sharing risks and rewards provides.

Northern Ireland had a devolved Parliament from its inception up until the beginning of the Troubles, after which it always remained UK Government policy to see devolved government there restored.

And when devolved government in Northern Ireland was finally restored, it was after an historic agreement to end a long and painful period of conflict.

The devolution settlement brought about by the Belfast Agreement was an example for the world in uniting people behind a shared future.

And as the parties in Northern Ireland continue in talks to restore that devolution, the hope and history surrounding it should be a powerful reminder of the imperative of not letting that progress slip away.

In Great Britain, successive Governments of both parties pursued policies of administrative devolution – the creation of separate Whitehall departments for Scotland and Wales, led by cabinet Ministers – but resisted calls for legislative devolution. There were objections to it from across the political spectrum.

Many on the left feared it would weaken the ability of a socialist government to effect economic and social change.

And, despite first making a Scottish Assembly our policy as early as 1968, many Conservatives worried that it might loosen the bonds that tie us together.

Both left and right are now fully united behind devolution.

A Labour Government created the devolved institutions in Scotland and Wales.

And Conservatives have embraced them.

Successive Conservative and Conservative-led governments since 2010 have strengthened the devolution settlements.

Holyrood has new powers over tax, welfare and more.

Cardiff Bay has tax powers and law-making powers.

In Northern Ireland we have legislated to enable Stormont to take on powers over corporation tax.

Today, the only threat to devolution comes from those parties who want to end it by breaking up the United Kingdom.

For those of us who believe in the Union, devolution is the accepted and permanent constitutional expression of the unique multinational character of our Union.

It was ironic that the UK Government’s sincere efforts to ensure that Brexit had no unintended consequences for the UK’s internal market was dismissed as a ‘power-grab’ by the SNP.

A UK Government which had enthusiastically launched and implemented the Smith and Silk Commissions – transferring sweeping powers over tax and welfare, stood accused of using Brexit as the cloak behind which to claw-back powers over food labelling and fertiliser regulations.

On one level the allegation is simply absurd.

On another, it highlights a challenge which faces the UK Government as it seeks to act in the best interests of the whole UK.

Whereas the UK Government is invested in the success of devolution, it would suit the political aspirations of the present Scottish Government for devolution to fail, or to be seen to fail.

The criticisms of the present First Minister about how our two governments interact need to be viewed in that context.

It is telling that during the discussions over legislative consent for the EU Withdrawal Bill, after intense discussions and give and take on both sides, the Welsh Government was willing to making a compromise, whereas the Scottish Government was not.

Over the last three years I have learned that while other parties can be relied on to work with the UK Government in good faith to make devolution a success, an SNP Scottish Government will only ever seek to further the agenda of separation.

That, I am afraid, is simply a fact of political life in the UK at the moment.

That fact puts an additional responsibility on the UK Government.

If we do not do all we can to realise the full benefits of the Union – no one else will.

If we do not use every policy lever within our reach to strengthen that Union – no one else will.

And if we do not make realising the full benefits of being a United Kingdom of four proud nations and one united people our priority now, then in the future it may be too late.

The answer does not lie in further constitutional change – or in reimagining what the Union is or should be.

Well intentioned suggestions that we should, for example, seek to agree a new Act of Union for the 21st century ignore the political reality.

With good will on all sides such a thing might be possible – but we do not have good will on all sides.

Many of those who advocate a federal UK are equally well-intentioned, but I believe are also in the wrong track.

England makes up over 80% of the UK population. There is no example of a federal state anywhere in the world where one of the units of the federation is so large.

The UK simply does not lend itself to federation as a sustainable constitutional model.

The only way it could realistically be achieved would be by breaking England up into artificial regional units – something I would never support and for which I detect no appetite.

Of course that is not to say that there is no appetite for devolution in England.

The UK Government has passed considerable power down to the great cities and metro-areas of England.

From Greater Manchester and the West Midlands to the Tees Valley and Bristol, there is now a new cast of powerful, directly elected local voices speaking up for their areas – voices which great cities like Glasgow and Cardiff lack.

So the answer to strengthening the Union does not lie in schemes of sweeping constitutional change, but in making better and more creative use of the powers and potential of the constitutional settlement we have.

The City and Growth Deals which the UK Government has pioneered across the United Kingdom – from Aberdeen to Swansea, Derry/Londonderry to the Borderlands – are examples of that creative thinking.

Working with the devolved administrations and local authorities as partners, they provide a vehicle for UK-wide engagement – each layer of government working together to drive better outcome for citizens.

The leadership election in my own party has encouraged a raft of suggestions for how the UK Government can play a more constructive role in realising the full benefits of the Union for all its people.

It has been a striking change at Westminster since the 2017 election that we now have a range of passionate and articulate Scottish voices across the House of Commons making constructive arguments about how to make the UK a better place.

But we will need to keep up this debate and for it to be informed by creative thinking and new ideas.

Tweaking the constitution is not the answer.

The UK Government already invests significant amounts across the nations of the UK, and the Barnett Formula rightly delivers higher public spending per head in Wales, Northern Ireland and Scotland – so spending alone is not the answer either.

Instead we need to look afresh at how we use the levers and the resources that are to hand through a Unionist lens.

We need to work more cleverly, more creatively and more coherently as a UK Government fully committed to a modern, 21st century Union in the context of a stable and permanent devolution settlement to strengthen the glue that holds our Union together.

There have been several reviews into how devolution works. But we have never thought deeply about how we make the Union work – how we ensure that as we fully respect devolution, we do not forget the UK Government’s fundamental duty to be a government for the whole United Kingdom of Great Britain and Northern Ireland.

That is why I have asked Andrew Dunlop to lead an independent review into the structures of the UK Government to ensure that they are set up to realise fully all the benefits of being a United Kingdom.

Lord Dunlop has a wealth of experience from his time in Government as an advisor and Minister and I look forward to reading his report.

Of course it will be for my successor to respond to his recommendations, and I am delighted that both candidates are supportive of the review.

I am confident that whoever succeeds me in 10 Downing Street will make the Union a priority.

He will build on the work of a UK Government that has made strengthening the Union an explicit priority.

The job of Prime Minister of the United Kingdom of Great Britain and Northern Ireland brings with it privileges and responsibilities which you only really feel once the black door closes behind you.

One of the first and greatest is the duty you owe to strengthen the Union.

To govern with the popular support on which that Union is based.

To respect the identities of every citizen of the UK – Scottish or Welsh, Northern Irish or English, British or Irish.

And to ensure that we go on facing the future together, overcoming obstacles together, and achieving more together than we ever could apart – as a Union of nations and people.