Theresa May will put forward a fresh offer to solve the Irish border dispute within hours, as the EU’s Brexit negotiator said Friday was the deadline to rescue a deal.

Michel Barnier put pressure on the Prime Minister by insisting diplomats of the 27 member states must sign off any potential agreement on Friday, if the talks are to move onto trade at a summit next week.

It set the scene for further frenzied negotiations between London, Brussels, Dublin and Belfast today to set down guarantees that a hard Irish border can be avoided after Brexit.

However, the Democratic Unionist Party signalled that it believed a deal was still some way off – with Arlene Foster, the DUP leader, yet to have face-to-face talks with Ms May.

Meanwhile, the Prime Minister was facing a growing civil war in her own party over her approach to the negotiations, as pro and anti-EU Tories traded insults.

Around 20 Conservative MPs wrote to the Prime Minister, urging her to stand up to “highly irresponsible” Brexiteer colleagues who want her to walk away from the negotiating table.

But Bernard Jenkin, a leading Eurosceptic, accused those MPs of being ready to vote down Ms May’s negotiating strategy – and turned his fire on Brussels for obstructing trade talks.

He dismissed concerns about a hard border and painted the Irish government as a Brussels pawn, saying: “Dublin is being used as a proxy by the European Union.”

Hopes of a deal rose after Leo Varadkar, the Irish Prime Minister, told Ms May he was willing to look at a new text and potentially shift Dublin’s position.

A deal fell apart on Monday when the UK’s pledge of “regulatory alignment” across Ireland – to avoid border customs checks and posts - was vetoed by the DUP.

Speaking in Dublin, Mr Varadkar suggested alignment need not apply to “everything”, but only to areas of “north-south” trading activity, and promised a “positive and open” attitude.

“I want us to move forward if it's possible next week,” he said. “It was a very good call. We were willing to look at any proposals the UK have.”

However, DUP sources said an agreement was far away, despite David Davis, the Brexit Secretary, saying regulatory alignment would apply across the UK, rather than treat Northern Ireland differently.

In Brussels, Mr Barnier agreed that EU ambassadors must discuss any proposed new agreement at a meeting on Friday evening, if it is to be on the table at the EU Council next Thursday.

The ambassadors want sufficient time to take it back to their capitals for scrutiny – or the summit is likely to rule that “sufficient progress” has not been made on the divorce issues.

A failure to agree to move onto trade talks would be a devastating blow for the Prime Minister, with business leaders increasingly angry at the damage looming.

It would also increase pressure from Tory Brexiteers for her to walk out of the talks and prepare for a “no deal Brexit”.