NICOLA Sturgeon has said the agreement on the Brexit divorce is a “welcome step forward” but that it kills stone dead the Unionist argument that Scottish independence would mean a hard border between Scotland and England.

The First Minister took to Twitter soon after news of the deal emerged.

“A UK Government that is able to say that come what may, it will avoid hard borders with Ireland/NI after Brexit can never again tell Scotland that independence would mean a hard border between Scotland and rUK,” she wrote.

READ MORE: What does the Brexit divorce deal really involve?

Scots Tory leader Ruth Davidson pounced on the tweet.

“And ... here we go,” Davidson tweeted back. “Right on time Nicola Sturgeon uses any Brexit development to bang the indy drum. Could set your watch by it. Give it a rest.”

The First Minister replied: “Democracy, Tory style – shut up and let us inflict whatever damage on Scotland we want.”

In the run-up to the 2014 referendum Theresa May, then Home Secretary, said the British Government would expect passport checks in the Borders if Scotland voted for independence.

“If the people of Scotland vote to leave the UK there would be profound changes for migration policy,” she said in a speech at the Scottish Tory conference in March 2014.

“Buried deep in Alex Salmond’s white paper is the admission that, just like the last Labour government, a separate Scotland would pursue a looser immigration policy.

“That would undermine the work we have done since 2010, and the continuing UK could not allow Scotland to become a convenient landing point for migration into the United Kingdom. So that would mean border controls between a separate Scotland and the United Kingdom.

“Passport checks to visit friends and relatives. A literal and figurative barrier between our nations.”

But the compromise reached on Ireland by the Prime Minister will mean no “literal” barrier on what will be the UK’s only land border with the EU.

In a statement issued later, Sturgeon said the Scottish people wished “Brexit was not happening and that the UK as a whole was not leaving the European Union,” but, “today’s proposed agreement is a welcome step forward in the negotiations.”

She added: “The next phase will be significantly tougher and it is essential all the UK’s governments are now fully involved in the negotiations on the UK’s future relationship with the EU – something that has not happened to this point.”

The First Minister welcomed the guarantee there would be no hard border on the island of Ireland and said the Scottish Government would seek clarity on how full alignment with the rules of the single market and customs union would be delivered.

She added: “I am absolutely clear that any special arrangements for Northern Ireland must now be available to other nations of the UK – the Scottish Government will not accept any arrangements which risk putting Scotland at an economic disadvantage. Short of continuing EU membership, the best outcome for jobs and living standards is to retain membership of the single market and customs union – both in transition and permanently.”

In her comments Davidson, who aligned herself with DUP leader Arlene Foster against the Prime Minister – said the development was “a real step forward”.

She said: “Throughout this process, my overriding priority has been to ensure we act as one United Kingdom and no home nation is left behind.

“I am therefore glad that this morning’s agreement ensures the integrity of the UK. The work on a comprehensive trade agreement with the EU27 can now begin. This will require more hard work and patience.”