British Prime Minister Theresa May | Julien Warnand/EPA Theresa May delays Brexit vote over risk of ‘significant’ defeat ‘I’ve listened very carefully to what has been said in this chamber,’ said the UK prime minister.

LONDON — The U.K. prime minister said a meaningful vote among MPs on her Brexit deal that had been scheduled for Tuesday will be deferred so that she can seek "further assurances" from EU leaders.

In a statement to the House of Commons she acknowledged the "widespread and deep concern” over the controversial Irish backstop, which is designed to avoid a hard border, admitting her deal would be rejected by a “significant margin” if the vote was held.

May said she would "discuss with them the clear concerns that this house has expressed," about the backstop with EU leaders in Brussels and with member countries.

After weeks of the prime minister and her Cabinet repeating the government line that the deal could not be reopened and that it was the best available, the move marks a significant climbdown. And with the clock ticking towards the U.K.'s departure from the EU on March 29 next year it leaves precious little time to find a solution.

EU leaders have shown no willingness to reopen the agreement that they endorsed at a special summit in Brussels last month, so the chances of May achieving meaningful changes to the deal that would assuage the doubts of skeptical backbenchers look slim.

"I have listened very carefully to what has been said, in this chamber and out of it, by members from all sides," May told MPs. "From listening to those views it is clear that while there is broad support for many of the key aspects of the deal, on one issue — the Northern Ireland backstop — there remains widespread and deep concern."

"I still believe there is a majority to be won in this House in support of it, if I can secure additional reassurance on the question of the backstop," she said, adding that ministers were also looking at new ways of “empowering the House of Commons” to ensure any provision for the backstop has democratic legitimacy.

May told MPs she was in “absolutely no doubt that this deal is the right one,” and believed there was a majority to be won in the house in support of it if she could secure additional reassurance on the question of the backstop. Controversial aspects of the deal, including the backstop, were “simply inescapable facts of having a negotiated Brexit,” she told MPs.

May's statement was followed by a highly unusual intervention by the speaker John Bercow, who said the delay would be "thought by many to be deeply discourteous," particularly since 164 MPs had already spoken in the debate.

He said that it would be "infinitely preferable" if the house were to have a vote on whether the meaningful vote on the Brexit deal should be delayed, rather than the government forcing that course of action unilaterally. In a "courteous, respectful and mature environment, allowing the House to have a say, its say on this matter, would be the right and dare I say it the obvious course to take," he added.

Opposition Labour leader Jeremy Corbyn said the delay was "shambolic" and had created an "extremely serious situation."

"The government has lost control of events and is in complete disarray," he said.

Nigel Dodds, the deputy leader of the Democratic Unionist Party who's MPs support the government under a confidence and supply agreement, said the prime minister's words were not "credible."

"Does [May] not get it by now that the withdrawal agreement, legally binding text, is unacceptable to this House." He urged the prime minister to "start listening" and to come back with changes to the Withdrawal Agreement itself, or it would be voted down.

May is “buying time hoping that people will come round under public pressure and EU might concede a bit more,” Sean Kelly, a member of the European Parliament from Ireland’s ruling Fine Gael party, told POLITICO.

Her course of action is, “in the circumstances, wise. But divisions are enormous,” he added.

One senior official from an EU27 country said that May's announcement “clearly shows the pressure exerted over her.”

“I don’t think she has anymore any chance to pass the deal,” this official added. Asked whether the chances of a no-deal Brexit are rising, the senior official said “I’m afraid so.”

Speaking earlier in the day, Irish Prime Minister Leo Varadkar said the deal could not be reopened. "The Withdrawal Agreement, including the Irish backstop, is the only agreement on the table. It took over a year and a half to negotiate, it has the support of 28 governments and it is not possible to reopen any aspect of that agreement without opening all aspects,” he said, according to the Irish Examiner.

Adam Marshall, the director general of the British Chambers of Commerce condemned the move to delay the vote. “Firms are looking on with utter dismay at the ongoing saga in Westminster, and express concern that politicians are seemingly acting in their own interest, with little regard for the millions of people whose livelihoods depend on the success of U.K. business and trade," he said.

"Many business leaders will be intensely frustrated by yet another delay in this drawn-out process, which impacts real-world business conditions, not least currency markets. Businesses are clear that time is rapidly running out."

Members of the House of Lords will go ahead as planned with a vote on the Brexit deal Monday evening.