Theresa May’s Brexit plan was dealt another major blow at a meeting with EU leaders on Thursday night in a disastrous turn of events that resulted in them scrapping written commitments to help her pass her deal through parliament.

After arriving in Brussels with promises to help the prime minister, European leaders were left amazed when she turned up without any developed requests or ideas.

The 27 heads of state and government subsequently decided to delete lines from their council conclusions saying the EU “stands ready to examine whether any further assurance can be provided” and that “the backstop does not represent a desirable outcome for the union”.

The key paragraphs appeared in leaked earlier drafts on the conclusions and their absence leaves a barebones statement that does the bare minimum to help the prime minister. The limited assurances provided in the statement are extremely unlikely to placate Ms May’s MPs, who have said they want major changes to the agreement.

Accounts of the meeting suggest the prime minister’s speech, in which she called for help to get the agreement “over the line”, was repeatedly interrupted by Angela Merkel asking her what she actually wanted from them.

Senior UK government officials admitted that the prime minister did not bring any documented proposals with her to the meeting.

The approach puzzled EU diplomats, who for days before the conference had said they needed to see what proposals Ms May had come up with before they could respond to her request for aid.

Jean-Claude Juncker, the European Commission president, said at a midnight press conference after the discussion: “I do find it uncomfortable that there’s an impression perhaps in the UK that it is for the EU to propose solutions.

“It is for the UK leaving the EU and I would have thought that it was rather more for the British government.”

In the margins of the summit the meeting is already being called “Salzburg 2.0” – a reference to a previous summit in September where the prime minister’s dinner speech also ended up accidentally hardening the EU position.

The statement issued by leaders warns that the withdrawal agreement “is not open for renegotiation”, but clarifying that the controversial backstop will “apply temporarily, unless and until it is superseded by a subsequent agreement” and that the EU will “use its best endeavours” to get it replaced quickly “so that the backstop would only be in place for as long as strictly necessary”.

They assured the UK it was EU’s “firm determination to work speedily” to replace it with a trade agreement.

The statement will be of little help to the prime minister, who is struggling to get her deal through parliament after a bruising confidence vote on Wednesday where over 100 of her own MPs said she should quit.

The prime minister had told EU leaders: “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 called on them to give her something that would “change the dynamic” in Westminster, adding: “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.”

European Commission president Jean-Claude Juncker and European Council president Donald Tusk at a midnight press conference following the meeting (AP)

Ms May is said to have asked for a legally binding 2021 deadline to end the backstop, but it was pointed out by leaders that this would contradict the fundamental principles of the agreement. When asked if the UK could propose a way around this, the prime minister was said to have no answer.

Arriving at the meeting the prime minister had downplayed hopes of an “immediate breakthrough”. But the performance on Thursday evening appears to have derailed the possibility of any further help down the road in the new year, which the EU seemed receptive to before the session got underway. Such plans could have taken the form of protocols or side-declarations to the treaty.

Earlier in the day German chancellor Angela Merkel had said: “I do not see that this withdrawal agreement can be changed.

“We can discuss whether there should be additional assurances, but here the 27 member states will act very much in common and make their interests very clear.”

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Austrian chancellor Sebastian Kurz, who is currently chairing the European Council, struck a more conciliatory tone, telling reporters: “We are ready to accommodate Theresa May. It’s not about pushing through maximum positions but to find a provision that is the best possible for both sides.”

Juha Sipila, the Finnish prime minister, told reporters that it would be “a little bit difficult” to give the PM legally binding assurances but that leaders wanted to try and help anyway.