LONDON — Facing the prospect of a humiliating defeat, Prime Minister Theresa May said on Monday that she would seek to postpone a parliamentary vote on her proposal for Britain’s departure from the European Union, throwing the process into disarray and highlighting her tenuous hold on power.
Parliament had been scheduled to vote on Tuesday on the agreement that Mrs. May reached with the bloc for Britain’s withdrawal, or Brexit — a critical moment in her political career and in the battle over an issue that has gripped British politics for nearly three years.
But weeks of bitter criticism and days of parliamentary debate had left no doubt that the plan would be soundly rejected by lawmakers, due in large part to objections over plans for dealing with the Irish border that pro-Brexit lawmakers say could potentially leave the United Kingdom tied to some of the bloc’s rules indefinitely.
“If we went ahead and held the vote tomorrow, the deal would be defeated by a significant margin,” Mrs. May said in an unscheduled address to Parliament on Monday afternoon, punctuated by jeers and laughter as she attempted to make her case. “We will therefore defer the vote scheduled for tomorrow and not proceed to divide the house at this time.”
Although the prime minister appears to have the authority to unilaterally postpone the vote, there was opposition to such a move, adding yet another layer of unanswered questions to a process already steeped in uncertainty. Some opponents of the deal were eager to stick to the schedule and deliver a resounding defeat to the bill and to Mrs. May.
“The government has lost control of events and is in complete disarray,” said Jeremy Corbyn, leader of the opposition Labour Party. “It’s been evident for weeks that the prime minister’s deal did not have the confidence of this house, yet she plowed on regardless, reiterating this is the only deal available.”
The British pound lost about 1 percent of its value against the euro and the United States dollar, falling to its lowest level in more than a year and a half.
Mrs. May said that the only obstacle to parliamentary approval was disagreement over the status of Northern Ireland, which under the deal could remain more closely tied to the European Union than the rest of the country.
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“There remains widespread and deep concern,” she acknowledged. But she insisted that the solution was not to alter the agreement, which she called “the best deal that can be negotiated,” but to keep trying to sell it to skeptical lawmakers, while seeking renewed assurances from Brussels about Northern Ireland. In hours of questioning that followed, some members of her party accused her of reneging on promises, while opposition lawmakers pressed for her to resign or call elections.
European Union officials have insisted that the deal, reached last month after lengthy negotiations, represents their final offer, and that the only alternative is for Britain to leave the bloc on March 29 without an agreement in place — an abrupt and chaotic prospect that officials on both sides of the Channel predict would be economically damaging.
“The Brexit withdrawal agreement is the only deal on the table between the E.U. and the U.K. and is not open to renegotiation,” said the Irish prime minister, Leo Varadkar.
Responding to the delayed vote, Guy Verhofstadt, the European Parliament’s representative in the Brexit negotiations, wrote on Twitter, “I can’t follow anymore.”
“This delay will further aggravate the uncertainty for people & businesses,” he wrote. “It’s time they make up their mind!”
John Bercow, the speaker of the British House of Commons, who rules on procedural matters, said there were two ways to defer Tuesday’s vote.
The preferable approach, he said, would be for the government to move to adjourn the debate and win a majority vote for that adjournment; the alternative would be for the government, on its own, to simply decline to move the day’s scheduled business for consideration, although he hinted that he opposed such an approach.
“Halting the debate after no fewer than 164 colleagues have taken the trouble to contribute will be thought by many members of this house to be deeply discourteous,” he said. “Indeed, in the hours since news of this intention emerged, many colleagues from across the house have registered that view to me in the most forceful terms.”
Mrs. May did not address the question directly, but officials said the government would act unilaterally rather than put the postponement to a vote.
Prime Minister Theresa May postponed a parliamentary vote on her plan for Britain’s departure from the European Union.CreditTim Ireland/Associated Press
What will happen next with Mrs. May’s government is uncertain, and may not become clear until after the prime minister attends a European Union summit meeting in Brussels on Thursday and Friday. Lawmakers have floated an array of possibilities, including a renewed effort to have Parliament approve her plan, an attempt within her own Conservative Party to topple her, a Labour call for a vote of no confidence, a snap general election, and a second popular referendum on whether to leave the bloc.
The leaders of the Scottish National Party, the Liberal Democrats and Plaid Cymru, a Welsh party, announced that if Mr. Corbyn asked for a vote of no confidence in Mrs. May, their parties would support it — though their votes, combined with Labour’s, would still leave such a motion short of a majority. For his part, Mr. Corbyn did not say what he would do.
The effort to postpone Parliament’s vote came after Mrs. May spoke with members of her cabinet and briefed them on her weekend discussions with other European leaders.
It also came hours after the European Union’s highest court ruled that Britain could legally cancel its decision to leave the bloc and remain a member under its current terms, throwing a lifeline to those who still hope to reverse the withdrawal.
The decision, from the European Court of Justice, confirmed a recommendation last week by one of the court’s senior legal advisers.
Dozens of Conservative lawmakers who want a more complete break with Europe were expected to join most opposition lawmakers in voting against Mrs. May’s deal, though how many members of her party would abandon her was uncertain.
Steve Baker, a member of the European Research Group, an alliance of pro-Brexit Conservative lawmakers, said that postponing the vote would amount to “essentially a defeat” of Mrs. May’s agreement with the European Union.
The terms of the agreement “were so bad that they didn’t dare put it to Parliament for a vote,” he said on Twitter. “This isn’t the mark of a stable government or a strong plan.”
The Conservatives hold 315 seats, just shy of a majority in the 650-seat Parliament. Mrs. May governs with the cooperation of the Democratic Unionist Party of Northern Ireland, which holds 10 seats and vehemently opposes the Brexit deal.
Analysts had said that the prime minister expected to lose the initial vote but hoped the margin would not be embarrassingly large. Her plan in that case, they said, was to win a few concessions from Brussels and return to Parliament for a second vote.
Mrs. May started the two-year exit process by invoking Article 50 of the European Union’s treaty in March 2017. She has vowed to carry out the will of voters, who narrowly approved withdrawal from the union in a 2016 referendum.
But the European Court ruled that Britain could withdraw its Article 50 submission before that date, as long as it did so in accordance with the country’s democratic and constitutional arrangements, and communicated the decision in writing. The reversal would not require the approval of the 27 other member countries, the court said.
The decision is a boost for those who still hope that Brexit can be stopped, particularly if Parliament votes against Mrs. May’s deal. It came a day after thousands of people gathered in London for competing protests by supporters and opponents of Brexit, demonstrating that the issue has lost none of its divisive potency.
Britain has received several special concessions as part of its current membership terms, including one that allows it to opt out permanently from any obligation to join the European Union’s single currency, the euro. It also gains a valuable rebate on some of its annual budget contributions.
Were it to remain in the bloc, these membership terms would be kept, the court ruled. The ruling was made under a special, expedited procedure because of the urgency of the situation.
The case was taken to the court by a group of politicians who want to keep a close relationship with the European Union, or to reverse Brexit, including Alyn Smith, a member of the European Parliament from the Scottish National Party. In a Twitter post, he described the judgment as a “total vindication.”
Even so, a decision to stop Brexit remains some way off. It seems likely that remaining in the union would require lawmakers to decide to hold a second referendum on whether to reverse the 2016 decision. So far, there is no obvious majority in Parliament for that step.
On Monday, Mrs. May was still trying to win further promises from the European Union in order to reassure some pro-Brexit British lawmakers who are worried that her deal could leave Britain beholden to some European Union rules indefinitely.
Michael Gove, the environment secretary, told the BBC on Monday that Britain had no intention of reversing its decision to leave the European Union.