Mrs. May is preparing to try one more time next week before she negotiates with the EU over an extension beyond the scheduled exit date of March 29, according to people familiar with the matter. Her hope is that lawmakers who want a pure break with the bloc will now see the deal she worked out as their least-bad option, fearing that a lengthy delay could lead to a preservation of closer ties or even a second Brexit referendum.
“It is time for responsibility,” said Brexit Secretary Stephen Barclay, addressing Parliament as he urged lawmakers on Thursday to side with the government. “It is time to act in the national interest.”
The government’s motion to delay Brexit by at least three months passed on Thursday by 412 votes to 202. The other 27 EU governments must unanimously agree to any extension, a matter they will consider at a summit in Brussels that starts next Thursday.
Mrs. May’s room for maneuver is shrinking fast. With Parliament imposing serial defeats on the prime minister, she is struggling to keep her lawmakers and even some members of her cabinet on her side. The greatest share of those opposing the motion to delay—188 of 202 votes—were members of her own party.
An amendment to allow lawmakers to take control over the Brexit process from the government failed by just two votes on Thursday.
Opposition Labour leader Jeremy Corbyn repeated his demand for a second Brexit referendum, calling for “a public vote, not as political point-scoring but as a realistic option to break the deadlock.”
With that, Mr. Barclay countered, Mr. Corbyn was “shredding the votes of 17.4 million people in this country,” a reference to the slim majority of Britons who expressed support for Brexit in the June 2016 referendum.
Mrs. May’s hope is that the threat of a long delay will encourage several dozen hard-line anti-EU lawmakers to swallow their objections and support it.
It could also encourage her political allies—the Democratic Unionist Party from Northern Ireland—to also finally come onside. Mrs. May has repeatedly warned that if her deal is ignored, there is a risk that Brexit might be canceled.
But a vote next week could prove a knife-edge event for Mrs. May, who has staked her leadership on being able to deliver Brexit. If her deal fails and a long extension ensues, Conservative lawmakers could revolt against her, as many did on Thursdayagainst the government’s plan to delay Brexit.
Mrs. May is set to go to Brussels next Thursday to request the extension from other EU leaders.
If her withdrawal deal were to be approved by Parliament by then, she would request the EU grant a short extension to June 30 to allow time to turn the exit process into law. Such a brief delay would be uncontroversial, EU officials say.
If the agreement has by then been rejected a third time, then a much longer extension could follow.
Donald Tusk, who as president of the European Council presides over EU summits, tweeted on Thursday that he would push leaders to consider a long extension “if the U.K. finds it necessary to rethink its #Brexit strategy and build consensus around it.”
The formal argument for a long extension—possibly one of more than 12 months—is that it would give U.K. politicians time to build a firm consensus on Brexit and allow both sides more time to prepare for Britain’s departure.
Mr. Tusk is also aware, officials say, that such a lengthy extension could open up new approaches, heightening the pressure on the strongly pro-Brexit wing of Mrs. May’s Conservative Party to accept the deal at hand.
But the matter isn’t settled among EU governments. Some governments, including Germany and the Netherlands, appear to back the option of a long extension if more time is granted, officials said.
The proviso would be that, according to EU law, the U.K. would have to participate in EU elections to form a new European Parliament that sits in July. Mrs. May has cited avoiding that vote, slated for late May and likely to spell trouble for both main political parties, as one more reason for Brexit supporters to back her deal.
Mr. Tusk has still to start a tour of capitals aimed at building a consensus around how to respond to a British extension request.
A first discussion among EU ambassadors and EU chief negotiator Michel Barnier on Wednesday morning showed no clear consensus over the duration of an extension, with countries including France skeptical of a long delay and even wary of allowing any extra time for the Brexit negotiations.
Diplomats are particularly concerned that an extension could allow Britain to continue to avoid hard decisions about the trade-offs that exist between a close economic partnership with the EU and preserving British sovereignty. Officials didn’t agree during Wednesday’s discussion on whether any extension should be a one-off.
EU officials say that if the U.K. settles on an agreement before the extension ends, it could leave the EU at an earlier date.