Theresa May has told EU leaders the withdrawal deal they have negotiated with the UK is “at risk”, if MPs’ concerns cannot be addressed.
The PM, who delayed a Commons vote on the deal this week in anticipation of a heavy defeat, said she still believed it “can be passed”.
But she urged EU leaders to work with her to “change the perception” of the controversial “backstop” plan.
Mrs May won a confidence vote brought by MPs unhappy with her Brexit policy.
She has vowed to listen to the concerns of the 37% of Tory MPs who voted against her and is hoping to “assuage” their concerns about the “backstop” plan in the withdrawal agreement, aimed at preventing the return of a hard border in Northern Ireland.
Critics say it would keep the UK tied to EU rules indefinitely and curb its ability to strike trade deals.
Conservative MPs have demanded changes to the backstop to make it clear that it could not last forever, and the UK could terminate the arrangement on its own.
Mrs May has been at a summit of EU leaders in Brussels to seek legal assurances from them that the backstop, if used, would be temporary.
The BBC’s political editor Laura Kuenssberg said one of the ideas being considered in Brussels was whether they could agree a “start date” for a future trade relationship between the UK and the EU after Brexit instead of an end date for the backstop.
In comments released by Downing Street on Thursday, Mrs May told EU leaders she firmly believed the deal could get through the Commons and told them: “Let’s work together intensively to get this deal over the line in the best interests of all our people.”
But she added: “We have to change the perception that the backstop could be a trap from which the UK could not escape. Until we do, the deal – our deal – is at risk.”
And she said it was in everyone’s interests for the deal to be “delivered in an orderly way and to get it done now” rather than “to run the risk of an accidental ‘no deal’ with all the disruption that would bring or to allow this to drag on any further”.
“There is a majority in my Parliament who want to leave with a deal so with the right assurances this deal can be passed. Indeed it is the only deal capable of getting through my Parliament,” she said.
MPs were due to have their “meaningful vote” on the withdrawal deal on Tuesday, but the government pulled the vote the day before, with Mrs May admitting it would have been “rejected by a significant margin” – with many of her own MPs expressing serious concerns about the backstop.
She then faced a confidence vote in her leadership triggered by 48 of her MPs angry at her Brexit policy, which they say betrays the 2016 referendum result. She won by 200 votes to 117 but said she had listened to the concerns of those who voted against her.
Downing Street has confirmed that MPs will not now vote on the deal before Christmas and said the vote would happen “as soon as possible in January”.
On Thursday, Mrs May told EU leaders: “Over the last two years, I hope that I have shown you that you can trust me to do what is right, not always what is easy, however that difficult that might be for me politically.”
She asked them to trust her judgement, adding: “There is a majority in my Parliament who want to leave with a deal, so with the right assurances this deal can be passed. Indeed, it is the only deal that is capable of getting through my Parliament.”
Mrs May took questions from the leaders of the 27 other EU states before leaving while they discussed their response over dinner.
The European Council conclusions on Brexit published on Thursday evening say the EU would use its “best endeavours to negotiate and conclude expeditiously a subsequent agreement that would replace the backstop, and would expect the same of the United Kingdom, so that the backstop would only be in place for as long as strictly necessary.”
In other words, the EU would continue trying to negotiate a trade deal with the UK even if the Irish backstop had been triggered at the end of the transition period. The Brexit withdrawal agreement only talks about “best endeavours” being used to reach an agreement during the transition period.
The EU says it will not renegotiate the backstop, but may agree to give greater assurances on its temporary nature.
Austrian Chancellor Sebastian Kurz, who holds the rotating EU presidency, suggested there could be a special Brexit summit in January to agree “additional assurances”.
But Irish premier Leo Varadkar said that while EU was keen to be “helpful”, some of the suggestions she had put forward were “difficult” and warned there could be no “unilateral exit clause” on the backstop.