Britain’s political crisis intensified on Sunday after its decision to leave the European Union, with the opposition Labor Party splitting into warring camps and Scotland’s leader suggesting that its local Parliament might try to block the departure.
Many Britons were left wondering whether there was a plausible way for the nation to reconsider its drastic choice.
The hostilities in the Labor Party broke out as the battle lines became clearer among the governing Conservatives, left in turmoil by the vote on the European Union and the subsequent announcement by Prime Minister David Cameron that he would resign once his party chose a successor.
Michael Gove, the justice minister and one of the leaders of the Leave campaign, threw his support to the former London mayor Boris Johnson, the most prominent figure in the anti-Europe movement.
Aides to Theresa May, the home secretary, who backed the Remain side in the referendum on Thursday, were calling legislators to seek their support to take on Johnson.
The British news media reported that close allies of Cameron were also working to stop Johnson, reflecting the sense of betrayal on Downing Street over Johnson’s decision to tie his political ambitions to the movement to leave Europe.
Other Cabinet ministers were considering whether to run, including Nicky Morgan, the education secretary, and Liam Fox, a former defense secretary.
Hanging over the jockeying for power was intensifying discussion of whether the British exit, or “Brexit,” might somehow be avoided or circumvented.
Secretary of State John F. Kerry plans to visit Brussels and London on Monday. Speaking in Rome on Sunday, he said the United States respected the will of the voters and urged Britain and the EU to manage their separation responsibly for the sake of global markets and citizens.
Kerry said he and President Obama, who had urged a vote to remain, were confident that ‘‘we will be able to work through this in a sensible way.’’
Cameron has said he will leave to his successor the decision on whether and when to begin formal divorce proceedings, and neither Johnson nor Gove has been demanding such a step, leaving open at least the possibility that Britain could negotiate new terms of membership with Brussels and hold another referendum.
Johnson said from the start of the campaign that a vote to leave would push European Union nations into a new negotiation with Britain to keep it in the bloc. Leaders on the Continent have little appetite at the moment for such a deal, and circumventing the clear will of British voters would appear politically problematic for whoever succeeds Cameron.
The stunning vote has upended politics and exacerbated ideological and regional strains in Britain, leaving the nation with no unifying figure, at risk of coming apart and facing jittery financial markets.
The turmoil spread on Sunday to the Labor Party, whose leader, Jeremy Corbyn, a leftist, now faces a challenge from members of Parliament who have never favored him.
Early Sunday, Corbyn abruptly fired his shadow foreign secretary — the party’s spokesman on foreign affairs — to try to head off a coup begun by some Labor members of Parliament disappointed with Corbyn’s lackluster campaign to keep Britain in Europe.
With the Conservatives in disarray and the possibility of another general election within the year, some Labor legislators see this as a good moment to try to dethrone Corbyn, 67, whom they think would lead the party to electoral disaster.
Over the course of Sunday, at least 11 of the Labor shadow cabinet’s 30 members, not counting the foreign secretary, resigned as a signal of their opposition to his leadership. Corbyn’s office insisted that he would remain party leader and would beat back any challenge by appealing to grass-roots Labor Party members who elected him overwhelmingly in the first place.
After newspaper reports about the planned coup against Corbyn, the shadow foreign secretary, Hilary Benn, telephoned him early Sunday to say he and other key legislators had lost confidence in Corbyn to lead the party to victory. Corbyn ended the call by firing him, Benn told the Press Association, a British news agency.
“Following the result of the EU referendum, we need strong and effective leadership of the Labor Party that is capable of winning public support,” Benn said. “In a phone call to Jeremy, I told him I had lost confidence in his ability to lead the party, and he dismissed me.”
Corbyn faces a vote of confidence called for on Friday, after the referendum, by two lower-ranking Labor legislators.
“If a general election is called later this year, which is a very real prospect, we believe that under Jeremy’s leadership we could be looking at political oblivion,” Margaret Hodge, who proposed the no-confidence motion, wrote in a letter to fellow Labor legislators.
Corbyn and his allies were reported to be organizing demonstrations in his support. On Sunday morning, his office issued a terse statement: “There will be no resignation of a democratically elected leader with a strong mandate from the membership.”
Adding to the confusion about how Britain would proceed, Scotland’s first minister, Nicola Sturgeon, said on Sunday that the Scottish Parliament might move to try to block the British exit from the European Union by withholding legislative consent.
“You’re not going to vote for something that is not in Scotland’s interests,” she said in one of numerous television interviews.
It was not clear that the devolved Scottish Parliament had the power to veto a British exit, with constitutional scholars in this country, which famously lacks a formal constitution, differing on the question.
“I find it hard to believe that there wouldn’t be that requirement,” Sturgeon said of the need for Scotland’s approval. “I suspect that the UK government will take a very different view on that, and we’ll have to see where that discussion ends up.”
Since the Scotland Act of 1998 binds the Scottish Parliament to act in accordance with European Union law, some argue that the Parliament’s consent would be required to leave. The same might hold true for the devolved assemblies of Wales, which supported Brexit, and Northern Ireland, which did not.
