NICOLA Sturgeon faces losing an important ally in her demand for a differentiated Brexit deal because of the Stormont crisis, a leading politics expert has warned.

Professor Michael Keating, professor of politics at Aberdeen University and director of the Centre on Constitutional Change based at Edinburgh University, said the collapse of the Belfast Assembly may impact on demands for a bespoke deal for Remain supporting parts of the UK.

Like Scotland, Northern Ireland voted to Remain and the country benefits substantially from its status inside the EU in terms of funding for major infrastructure projects and its open border with the Irish Republic, also in the bloc.

Keating said the absence of any Stormont figures in the Joint Ministerial Committee, the body set up by Prime Minister Theresa May to get the input on Brexit from the devolved governments, will mean Scotland will have no ally on the Remain side, as Wales supported Leave.

“The potential was there for Northern Ireland to be an ally of Scotland in getting a differentiated Brexit settlement. Wales voted to Leave and Northern Ireland like Scotland was arguing for a differentiated deal for the devolved territories,” he said.

“Because of the Stormont crisis Scotland may no longer have this ally in Northern Ireland.”

Keating added the crisis added an additional layer of complication to the Brexit process.

“There is the whole question of how Northern Ireland fits into the Brexit process. There is the question of the Border, the north-south dimension. Important decisions will be made over the next few months and the Northern Ireland executive will not be there to have its voice heard.”

Keating’s comments on the lack of input from Northern Ireland on Brexit were echoed by the SNP’s Deidre Brock.

The Edinburgh MP pressed Secretary of State James Brokenshire on the issue in the Commons yesterday.

“Now that there is no effective administration at Stormont who can speak up for Northern Ireland in the Joint Ministerial Committee, and remembering that Northern Ireland voted to remain, can he tell us what he is doing to ensure that the interests of the people of Northern Ireland are being looked after when Brexit negotiations are considered?” she asked.

Stormont’s Deputy First Minister Martin McGuinness resigned on Monday signalling the end of an historic power-sharing administration in Northern Ireland.

He resigned over a botched green energy initiative, set up by the DUP First Minister Arlene Foster when she was Economy Minister.

Sinn Féin and other parties had called for Foster to step aside while an inquiry got underway to investigate how the scheme had overspent by £400 million. But Foster refused.

His resignation means the imminent collapse of the fragile government as under power-sharing rules the Unionist supporting DUP cannot govern without the support of the nationalist Sinn Féin.

Sinn Féin has seven days to re-nominate a new deputy first minister following McGuinness’ resignation. However, the party is adamant it will not replace him, meaning an end to the executive.

It is likely that next Monday the Conservative Northern Ireland Secretary James Brokenshire will be put in charge with the onus on him to call a new election to the Assembly. It is unclear when that would be and if a new Assembly would be in place before Article 50 is triggered.

Last month Sturgeon set out options for the whole of the UK to stay in the single market, and for Scotland to remain in it should the rest of the UK opt for a so-called “hard Brexit” out of it.

She said she hoped the UK Government would back a separate Scottish deal and that it would find support within Europe.

The terms of the UK’s Brexit deal must be agreed by each of the remaining 27 members.

A Scottish Government spokeswoman said: “Brexit is by far the biggest threat to Scotland’s jobs, prosperity and economy, which why we have always been clear that remaining members of the EU – and members of the world’s largest single market of more than 500 million people, which is around eight times bigger than the UK’s alone – is the best option for our future.

“The proposals we published last month are designed to keep Scotland in the single market even if the rest of the UK leaves – and we welcome the UK Government’s commitment to give them serious consideration in line with previous commitments.”