Theresa May signalled Brexit talks will continue over Christmas as she arrived in Brussels to try and win concessions to save her beleaguered withdrawal deal.

The prime minister arrived at the two-day EU summit having survived a leadership challenge by Tory MPs, hoping to get “reassurances” on the so-called Irish backstop which has turned the Commons against her deal.

Before the confidence vote – which she won by 200 votes to 117 – May had told Tories she was seeking a “legal assurances” over how the UK can exit the backstop plan for a customs union with the EU, amid fears the country could become trapped in it with no escape route.

But she played down expectations of an “immediate breakthrough” as Downing Street confirmed the ‘meaningful vote’ on the Brexit deal would be delayed until next year but come “as soon as possible in January”.

There was a glimmer of hope for May as Austrian chancellor Sebastian Kurz told his country’s Der Standard newspaper it was “possible” the EU could call another special Brexit summit in January to agree “additional assurances” which could be attached to the deal.

However, she was also warned by a series of EU leaders including Mr Kurz, who holds the rotating presidency of the council of the EU, and German chancellor Angela Merkel that the legally binding withdrawal agreement cannot be reopened.

Irish premier Leo Varadkar said after a lengthy one-to-one meeting with the PM the backstop is not on the table for renegotiation.

He said: “If the backstop has an expiry date, if there is a unilateral exit clause, then it is not a backstop. That would be to render it inoperable.

“That would mean reopening the substance of the withdrawal agreement and the European Union is unequivocal that is not an option.”

Tortured negotiations over the Irish backstop held up a deal between the UK and EU before it was struck last month and the return to the issue could spark fears of a similar cycle in the Brexit process. The PM’s official spokesman at the time dismissed an article about talks being stuck in a ‘doom loop’.

At the European Council summit in Brussels, May said: “My focus now is on ensuring that I can get those assurances that we need to get this deal over the line, because I genuinely believe it’s in the best interests of both sides – the UK and the EU – to get the deal over the line, to agree a deal.

“But I recognise the strength of concern in the House of Commons and that’s what I will be pushing to colleagues today.

“I don’t expect an immediate breakthrough, but what I do hope is that we can start work as quickly as possible on the assurances that are necessary.”

The PM also confirmed she would not lead the Tories into the next general election, an admission she made last night to MPs in what was seen as a necessary move to survive the confidence vote.

But May declined to name a date for her departure.

“I have said that in my heart I would love to be able to lead the Conservative Party into the next general election,” she said.

“But I think it is right that the party feels that it would prefer to go into that election with a new leader.”

Asked whether she had a date in mind to stand down, the PM went on: “No. People try to talk about dates.

“What I’m clear about is the next general election is in 2022 and I think it’s right that another party leader takes us into that general election.”

May will have a chance to address and answer questions from the other 27 EU leaders, but will leave after dinner to allow them to discuss Brexit privately.

Arriving at the summit, Dutch prime minister Mark Rutte said he respected May and criticised Labour MPs for laughing at her in the Commons on Monday when she announced she was pulling the vote on her deal.

He told reporters: “I feel respect, I admire her tenacity, she’s a great leader and when I saw some of the Labour people laughing at her when she said she had listened I thought that was not very British”.

Meanwhile, Jeremy Corbyn faced intensifying calls to clarify Labour’s Brexit policy amid pressure to back a second referendum, or so-called People’s Vote.

Activist group Open Labour backed calls from the TSSA union for an emergency special conference to give members a say over what the party will pitch to voters in any snap election.

Leeds North West MP and Open Labour committee member Alex Sobel said:

“Our internal democracy is the most vital part of our party decision making process. When facts change, it’s important to go back to our sovereign policy making body, Labour Party Conference, to make the decisions.

“With March 29 2019 rapidly approaching, it’s important that our members have the final say in what our position should be before a General Election.

“We all understand that our leadership is managing a very difficult balancing act well.

“I hope that they will see our members as vital in getting our party to stand united at this time of crisis and get the best resolution for our party, the communities we represent and everyone in this country, whether they voted leave or remain.”