European Union leaders have said the Brexit withdrawal agreement is “not open for renegotiation”, despite appeals from Theresa May.
She wanted legal assurances on the Irish backstop to help her deal get through Parliament, after she delayed a Commons vote in anticipation of defeat.
The PM said the deal was “at risk” if MPs’ concerns could not be addressed.
European Commission president Jean-Claude Juncker said there could be clarifications but no renegotiation.
He urged the UK to set out more clearly what it wants, adding that the commission will publish information on 19 December on its preparations for a no-deal Brexit.
Mrs May travelled to Brussels to make a special plea to EU leaders at Thursday’s summit, but BBC Brussels reporter Adam Fleming said some diplomats described her performance as “bad” and “vague”.
He added that a diplomatic note about proceedings, seen by the BBC, said Mrs May was “not really clear”.
Shadow Brexit secretary Sir Keir Starmer said Mrs May had failed to get meaningful changes and she should reinstate the vote on her deal next week.
The PM’s visit came at the end of a week that has seen her first delay the vote on the withdrawal agreement in Parliament, then win a vote of no confidence brought by MPs unhappy with it.
She vowed to listen to the concerns of the 37% of Tory MPs who voted against her, and was hoping to “assuage” their concerns about the controversial “backstop” plan in the agreement.
Critics say the backstop – aimed at preventing a hard border in Northern Ireland – would keep the UK tied to EU rules indefinitely and curb its ability to strike trade deals.
Conservative MPs 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.
At the summit, Mrs May was seeking legal assurances 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.
If this meeting in Brussels was meant to provide Theresa May with the beginnings of an escape route from her Brexit conundrum, the signs are not good.
At one of her most vulnerable political moments, Number 10 was hopeful at least of an indication of a potential solution to the most intense of a long list of Brexit problems – the controversial so-called backstop designed to guarantee against a hard Irish border.
But right now, that’s simply not on offer.
EU leaders made plain their warnings that their divorce deal with Britain was not up for negotiation were real.
Requests for change to ease Westminster politics were not fulfilled, with key phrases from a more accommodating draft gone by midnight.
But the rejection gives succour perhaps to those in government who want their critics to accept that the prime minister’s deal may be genuinely, as good as it gets.
In comments released by Downing Street on Thursday, Mrs May told EU leaders she firmly believed the deal could get through the Commons, saying: “Let’s work together intensively to get this deal over the line in the best interests of all our people.”
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.
“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 difficult that might be for me politically.”
Mrs May urged EU leaders to work with her to “change the perception” of the controversial backstop plan.
European Council president Donald Tusk said the withdrawal agreement was “not open for renegotiation”.
But speaking after the Brussels summit, Mr Tusk called the backstop “an insurance policy,” saying it was the EU’s “firm determination” to work “speedily” on alternative arrangements.
Mr Tusk said the backstop would “apply temporarily unless and until it is superseded by a subsequent agreement that ensures that the hard border is avoided”.
Mr Juncker also urged the UK to tell the EU what it wants from a future relationship.
“Our UK friends need to say what they want, instead of asking us to say what we want, and so we would like within a few weeks our UK friends to set out their expectations for us, because this debate is sometimes nebulous and imprecise and I would like clarifications,” he said.
The European Council’s 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 words that diplomats were using about Theresa May’s performance were “bad” and “vague”.
However, she did get something.
She got a recommitment from the EU that they want a close future relationship and will work quickly to get that.
There was also a recommitment that the backstop was temporary.
The fact the EU said it would use its best endeavours to get a future trade deal that would get rid of the need for a backstop – even if the backstop came into force – was seen as important by British officials.
They say it means the UK could go to an independent arbitration panel if they feel the EU is dragging its feet.
That was a win for them.
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 the EU was keen to be “helpful”, some of the suggestions Mrs May had put forward were “difficult”, and he warned there could be no “unilateral exit clause” on the backstop.