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

In the aftermath of Thursday’s Brexit vote, Britain and other nations prepared for more potential financial shocks when markets open today after Friday’s worldwide sell-off.

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

Cameron’s decision to hand off to his successor the matter of how to exit the EU 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.

Sunday began with news that Labour Party leader Jeremy Corbyn had fired one of the most senior members of his leadership team, Hilary Benn, after Benn had 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-in-waiting. By late in the day, nine others had quit their positions in what amounted to a rolling repudiation of Corbyn’s leadership.

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

Corbyn faces a vote of no confidence among his parliamentary peers this week. The Labour members of Parliament who offered the motion, Margaret Hodge and Ann Coffey, sent a letter to their 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 was elected just a year ago with overwhelming support from rank-and-file members of the party. That base still appears strong, setting up the possibility of a disastrous civil war between the party’s progressive grassroots and many elected leaders from Labour’s centrist wing, and others.

The fate of Corbyn, however, is 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 he wants to see a successor in place by early October.

Boris Johnson, the flamboyant former mayor of London and the leading voice in the campaign to exit the EU, is considered the favorite, but he is a magnet for controversy. Newspapers Sunday were filled with reports of gathering efforts by other Conservatives to deny him the post.

Nicola Sturgeon, head of the Scottish National Party, continued to press for a new independence referendum, a move that could lead to the dismantlement of the United Kingdom.

Scotland’s voters rejected such a referendum in 2014 but Sturgeon said Sunday on BBC Scotland, “The U.K. that Scotland voted to remain within in 2014 isn’t there anymore.”