The UK Government’s deal with the DUP to restore powersharing at Stormont includes plans to extend a low-regulation, low-tax “enhanced investment zone” to cover Stranraer and Cairnryan.

A Scotland Office source described it as “a huge jobs and investment boost.”

The promise was part of a command paper titled “Safeguarding The Union” put forward by ministers in Whitehall following months of negotiations to try and restore power-sharing in Northern Ireland.

The DUP has refused to take part in the devolved government in protest at the Northern Ireland protocol agreed by Boris Johnson that effectively avoided a border on the island of Ireland by putting it in the Irish Sea instead.

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The key proposal to break the stalemate is an end to routine checks on goods crossing the North Channel and Irish Sea but remaining in the UK, replacing the “green lane” with a “UK internal market system".

The command paper also includes a promise of a £150m “Northern Ireland Enhanced Investment Zone.”

It says this new area “will ensure that Northern Ireland benefits from a policy that has been applied elsewhere in the UK, and provide targeted incentives and interventions to encourage investment and boost growth".

The paper goes on to say the government will “will also pursue and engage through the East-West Council on the scope to extend Investment Zone benefits to the Stranraer/Cairnryan area in Scotland - recognising this vital Union connectivity route and boosting growth".

A UK Government source said: “This will be a huge jobs and investment boost for south west Scotland. Alister Jack has been the driver behind this exciting proposal which will strengthen Scotland’s economic ties with Northern Ireland and benefit the whole United Kingdom.”

MPs will be asked to vote on the new legislation on Thursday, with an ambition to get power-sharing up and running by the end of the week after two years of deadlock.

The command paper also includes commitments to ensure Northern Ireland goods will always be able to be sold in Great Britain regardless of any divergence in EU and UK standards.

A requirement that saw certain goods sold in Northern Ireland to display a label stating “not for sale in the EU” will now extend to cover the whole UK.

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While Sir Jeffrey Donaldson has secured significant movement from the UK Government, his party is not united.

Speaking in the Commons, East Antrim MP Sammy Wilson said: “When the Northern Ireland Assembly sits, ministers and Assembly members will be expected by law to adhere to and implement laws which are made in Brussels, which they had no say over and no ability to amend, and no ability to stop,” he said.

“This is a result of this spineless, weak-kneed, Brexit-betraying Government, refusing to take on the EU and its interference in Northern Ireland.”

Rishi Sunak was more optimistic. He told the Commons: “After two years without an executive, there is now a prospect of power-sharing back up and running, strengthening our union, giving people the local, accountable government that they need, and offering a brighter future for Northern Ireland,” he said.

Labour’s shadow Northern Ireland secretary, Hilary Benn, said it was “our chance to restore to the people of Northern Ireland that which they desperately need but have been without for almost two years: a functioning government”.

The DUP leader, Jeffrey Donaldson, said the package would restore Northern Ireland’s place in the UK and its internal market. “The border in the Irish Sea is removed,” he told the BBC.

If, as looks likely, Stormont is reconvened on Saturday, Sinn Féin’s Michelle O’Neill will become first minister, with a DUP member as deputy.

Ms O’Neill said the partition of the island of Ireland had “failed” its people. “The very fact that for the first time someone from Sinn Féin, a nationalist, a republican woman from Tyrone, will be first minister – that speaks to the change that’s happening,” she said.