People walk over Westminster Bridge wrapped in Union Jacks, toward the Queen Elizabeth Tower (Big Ben) and the Houses of Parliament in central London.

June 26, 2016 People walk over Westminster Bridge wrapped in Union Jacks, toward the Queen Elizabeth Tower (Big Ben) and the Houses of Parliament in central London. Odd Andersen/AFP/Getty Images

In late June, many celebrated the referendum results, and British Prime Minister David Cameron announced that he will resign after Britons went to the polls.

Many celebrated the referendum results Friday and British Prime Minister David Cameron announced that he will resign after Britons went to the polls the day before.

Many celebrated the referendum results Friday and British Prime Minister David Cameron announced that he will resign after Britons went to the polls the day before.

The political fallout from Britain’s stunning decision to leave the European Union sharply escalated Sunday, with debate growing inside the governing Conservative Party over choosing a successor to Prime Minister David Cameron and a coup attempt emerging against the leader of the opposition Labour Party.

The day was marked by a succession of fast-moving events against the backdrop of a leadership crisis in the aftermath of Thursday’s Brexit vote. The political maneuvering came as Britain and other nations prepared for more potential financial shocks when markets open on Monday after Friday’s worldwide sell-off.

The turmoil here underscored the degree to which the decision to break with Europe — an action seen widely here as the most significant event in the postwar history of Britain — has left the country politically divided, deeply unsettled and in uncharted territory on multiple fronts.

[Millions of Brits signed a petition for another E.U. referendum]

The complex process of negotiating the terms of the separation from the European Union has suddenly collided with a leadership crisis triggered by a voter revolt against the nation’s political establishment.

In a stunning victory for the “leave" campaign, Britain has voted to exit the European Union. Here's what happens next. (Jason Aldag,Adam Taylor/The Washington Post)

The decision by Cameron to hand off to his successor the issue of how to exit the E.U. and the absence so far of any concrete plans advanced by the government or by leaders of the “leave” campaign who could inherit that responsibility have heightened the uncertainty and increased tensions across the political spectrum.

Sunday opened with news that Labour Party leader Jeremy Corbyn had fired one of the most senior members of his leadership team, Hilary Benn, after Benn told the leader he had lost confidence in him.

The sacking of Benn led to a succession of resignations by other members of the Labour cabinet. By late in the day, at least 10 others had quit their positions in what amounted to a rolling repudiation of Corbyn’s leadership by his elected colleagues.

On Sunday night, Corbyn again said he would not be pushed out. “I am not going to betray the trust of those who voted for me,” he said.

The Labour revolt reflected fears that the party could suffer what Benn called a “catastrophic” defeat if, as expected, there is a general election called this year after the Conservative Party chooses a leader to succeed Cameron.

“He’s a good and decent man, but he is not a leader,” Benn said of Corbyn during an interview with the BBC’s Andrew Marr. “That’s the problem.”

Corbyn faces a vote of no confidence among his parliamentary peers this week. The two Labour members of Parliament who offered the motion, Margaret Hodge and Ann Coffey, sent a letter to colleagues expressing pessimism about the party’s future under Corbyn. “If a general election is called later this year . . . we believe that under Jeremy’s leadership we could be looking at political oblivion,” they said.

Corbyn has vowed to stand firm against efforts to oust him and began to rally a counter movement to fend off the coup attempt. As the resignations came one after another Sunday, his allies rushed to his defense, with more shows of support planned in coming days.

Corbyn was elected just a year ago with overwhelming support from rank-and-file members of the party. That base still appears to be strong, despite the defections among elected leaders, setting up the possibility of a disastrous civil war between the party’s progressive grass roots and many elected leaders who come from Labour’s centrist wing and others.

The fate of Corbyn, however, is currently seen as secondary to the question of who will lead the Conservatives, as that person will immediately become prime minister upon Cameron’s official resignation. Cameron said Friday that he wants to see a successor in place by early October.

Boris Johnson, the former mayor of London and the leading voice in the campaign to exit the E.U., is considered the favorite to take over from Cameron. But the flamboyant Johnson is a magnet for controversy. Newspapers Sunday were filled with reports of gathering efforts by other Conservatives to deny him the post he has long been maneuvering to claim.

[Media reacts to Brexit: ‘Welcome to Boris Island’]

Despite Johnson’s position as the Conservative front-runner, the leadership contest could end up with a number of candidates seeking to block his path. One potentially strong challenger is Theresa May, currently the home secretary and a quiet campaigner in favor of Britain remaining in the E.U. But some Tory leaders say the next prime minister should come from the party’s pro-Brexit wing.

Cameron has been largely invisible since he emerged Friday morning to announce his intention to resign. So, too, has his ally George Osborne, the finance minister. He is the architect of the government’s economic policies and is regarded as a key player in dealing with the economic and budgetary fallout from Brexit. But his hopes of becoming prime minister have taken a beating because of the Brexit decision.

The most visible leader in Britain in the days since the vote has been Nicola Sturgeon, Scotland’s first minister and the head of the Scottish National Party. On Sunday, she continued to press for a new independence referendum, a move that could lead to the dismantlement of the United Kingdom. Scotland’s voters rejected a similar referendum in 2014. But “the U.K. that Scotland voted to remain within in 2014 isn’t there anymore,” Sturgeon said Sunday on BBC Scotland.

[Scottish leader threatens a second independence referendum]

Scotland voted strongly to remain in the E.U. Sturgeon has said she would seek negotiations directly with European leaders in Brussels in an effort to keep Scotland in the E.U. as a way to protect the region’s economic interests.

A query to the E.U. offices about the possibility of Scotland negotiating separate standing produced a text reply from spokesman Daniel Rosario: “Scotland is part of the U.K.,” he said. “The respective constitutional arrangements apply. We will not speculate further.”

Sturgeon on Sunday also raised the possibility of the Scottish Parliament blocking Britain from leaving the E.U., but other officials said that they doubted that was within the powers of the Scottish body and that withholding consent would not amount to a veto.

Since Thursday’s vote, European leaders have pushed back against Cameron’s desire to delay triggering the process of withdrawing from the E.U. under the bloc’s Article 50. On Saturday, foreign ministers from the six original members of the E.U. spoke as one in calling on Britain to get moving “as soon as possible.”

German Chancellor Angela Merkel, however, offered a softer tone, suggesting more patience over the timing of the start of the divorce proceedings.

Amid the public pressure from Europe for Britain to quickly trigger Article 50, there were also suggestions that continental leaders believed hope was not yet lost.

In an interview with the Redaktionsnetzwerk Deutschland newspaper published Sunday, Merkel’s chief of staff, Peter Altmaier, said politicians in London should be given an opportunity to reevaluate the “consequences” of exiting the bloc, suggesting the Germans believed there might still be a chance to keep Britain in the fold.

[Who could be next?]

The posture of the European leaders could become clearer this week during a series of scheduled meetings. On Monday, Merkel, French President François Hollande and Italian Prime Minister Matteo Renzi plan to huddle in Berlin to coordinate their demands for Britain ahead of a Tuesday summit of all 28 E.U. leaders in Brussels.

Cameron will be present for that Tuesday meeting and will no doubt be asked to explain himself over what could be a foul-spirited dinner. On Wednesday, the leaders will kick Cameron out of the room and discuss how to handle what will probably be years of torturous divorce negotiations.

[European power suddenly shrinks]

President Obama spoke with Cameron on Friday, and in the subsequent days there have been multiple conversations between administration officials and their European and Asian counterparts about the economic and security implications of the Brexit vote. The United States has taken no position on how quickly the divorce proceedings should begin.

Secretary of State John F. Kerry plans to visit Brussels and London on Monday. Speaking in Rome on Sunday, he said that the United States respects the will of the voters and that he and Obama, who had urged a vote to remain, were confident that “we will be able to work through this in a sensible way.”

Faiola reported from Berlin, Birnbaum from Brussels.

Read more:

Would a break from Brussels also splinter Britain? Probably not.

Why North America won’t copy European unity

Despite assurances, immigrants in Britain are uncertain of their future

Today’s coverage from Post correspondents around the world