AN embattled Theresa May has insisted a Brexit deal is still “achievable” despite deadlock in negotiations and increased speculation the UK could crash out without one.

Just days ahead of a crunch European Council summit the Prime Minister called for “cool, calm heads to prevail” after talks last weekend failed to bridge differences between the UK and EU over the future status of a so-called backstop plan to prevent a hard Border in Ireland.

She warned of the danger that failure to reach agreement over the issue could result in the UK leaving the EU without a deal in March next year.

The Prime Minister was addressing the House of Commons just two days before she travels to Brussels for a summit at which it had initially been hoped to finalise the UK’s withdrawal agreement as well as a political declaration on future trade and security relations.

Following the failure to achieve a breakthrough when Brexit Secretary Dominic Raab met EU chief negotiator Michel Barnier on Sunday, the European Commission confirmed no further negotiations will be held ahead of tomorrow’s summit.

German Chancellor Angela Merkel said the prospect of agreement “looks a bit more difficult again”, adding: “If it doesn’t work out this week, we must continue negotiating, that is clear – but time is pressing.”

Berlin wants the UK’s withdrawal next March to be orderly “but not at any price”, Merkel told a conference of German exporters.

And Irish Taoiseach Leo Varadkar suggested a deal may be delayed as late as December. Varadkar said Dublin was making preparations for a “potentially catastrophic” no-deal withdrawal, but did not believe that this was the most likely outcome.

Sammy Wilson, Brexit spokesman for the DUP, which props up May’s minority administration, said a no-deal outcome was now “probably inevitable” due to the “intransigence” of EU negotiators.

Talks at the weekend foundered over the EU’s demand for a “backstop to the backstop” designed to ensure that the border between Northern Ireland and the Republic remains open under any circumstances. May has offered to keep the whole of the UK temporarily in a customs union with the EU until a wider trade deal is in place avoiding the need for customs and regulatory checks at the border, with the expectation that this will not be later than the end of 2021. But Barnier insisted a carve-out keeping Northern Ireland alone in the EU’s customs area should be available in case the UK-wide arrangement lapses before the trade deal is finalised.

May told MPs that this was not acceptable, saying it risked undermining the integrity of the UK. The PM warned the Irish issue must not be allowed to “derail” progress towards a deal which she said was in the interests of both the UK and EU. She told MPs she would take steps to ensure “we cannot be kept in this backstop arrangement indefinitely”.

She warned: “We are entering the final stages of these negotiations. This is the time for cool, calm heads to prevail. We cannot let this disagreement derail the prospects of a good deal and leave us with the no-deal outcome that no-one wants.

“I continue to believe that a negotiated deal is the best outcome for the UK and for the European Union.

“I continue to believe that such a deal is achievable.”

Labour leader Jeremy Corbyn dismissed May’s comments as “another ‘nothing has changed’ moment from this shambles of a Government”.

Peter Grant, the SNP’s Brexit spokesman, said the UK government had shown “at best disdain and at worst open contempt for the Good Friday Agreement” which helped end the Troubles.

The impasse threatens to throw into disarray carefully choreographed plans which would have seen leaders of the remaining 27 EU states give the green light tomorrow to a special summit in November to finalise the terms of the UK’s withdrawal from the bloc.

Reports suggest that the EU27 are now considering using the November summit to discuss preparations for a no-deal Brexit.

The febrile atmosphere in the Tory ranks has seen former Brexit secretary David Davis emerge as a potential successor to May.