Dozens of Labour Party lawmakers called on Prime Minister Keir Starmer to resign on Monday, effectively rejecting the British leader’s efforts to quell a mutiny in his own party’s ranks and raising the likelihood of a bruising leadership battle.
Mr. Starmer began the day with a speech he hoped would quiet the brewing rebellion, acknowledging the anger expressed by voters last week when they overwhelmingly rejected Labour Party candidates in elections across England, Scotland and Wales.
“That hurts and it should hurt,” he said. “I get it. I feel it. And I take responsibility.”
But the speech appears to have done little to appease Labour Party members who blame Mr. Starmer’s deep unpopularity with voters for historic defeats in the contests for municipal council seats and control of the Scottish and Welsh parliaments.
By the end of the day on Monday, news organizations had tallied more than 70 Labour lawmakers who publicly said they wanted a fresh start. Several junior government aides resigned to protest his decision to stay on.
Critics of the prime minister must gather 81 signatures on a petition supporting a single challenger to trigger a formal leadership election, which could force Mr. Starmer out of office. It was unclear whether any single challenger was close to being able to assemble that many supporters.
But the public rejection of Mr. Starmer’s two-year tenure snowballed throughout the day, vastly increasing the political peril for him even as he vowed to stay in his job.
Officials said Mr. Starmer would meet with his cabinet on Tuesday morning amid reports from multiple British news outlets, including the BBC, The Times of London and The Guardian, that several of his ministers are telling him that his political position is unsustainable and that he should consider setting out a timeline for stepping down.
Losing the support of key aides and members of his cabinet would be a heavy blow to Mr. Starmer, who has previously been criticized largely by backbenchers in Parliament, not members of his own cabinet.
Mr. Starmer and his allies argued throughout the day on Monday that a change in leadership would mean chaos for the country, making reference to the succession of prime ministers from the Conservative Party, known as the Tories, in the years before Labour had won the general election in 2024.
“I take responsibility for not walking away,” Mr. Starmer said in his morning speech. “Not plunging our country into chaos, as the Tories did time and again. Chaos that did lasting damage to this country. A Labour government would never be forgiven for inflicting that on our country again.”
In a white button-down shirt with no tie or jacket, Mr. Starmer, who is often described as a wooden speaker, offered moments of emotion, voicing both contrition for his mistakes and a commitment to Labour values. He talked about his late brother, who had learning difficulties and struggled to stay employed, and his sister, who he said worked long hours for little pay, to emphasize his belief that he understood ordinary voters’ frustration.
But he offered only vague descriptions of his new agenda, which mostly appeared to restate his existing approach. He repeated his desire to move the country closer to Europe but offered few specifics as to how that would happen. He said he would continue making it easier for young people to find jobs. He called hate and division “nothing less than a battle for the soul of our nation.”
“We cannot win as a weaker version of Reform or the Greens,” he said, referring to Reform U.K., the right-wing populist party led by Nigel Farage, and an insurgent Green Party. “We can only win as a stronger version of Labour.”
Shortly after the speech, Catherine West, a Labour lawmaker who over the weekend had said she would attempt to trigger an immediate leadership challenge on Monday, retreated a little from her initial threat. She asked instead for support from colleagues to pressure Mr. Starmer to set a timetable for his departure.
“I have reluctantly concluded that this morning’s speech was too little, too late,” she said in a statement, adding: “What is best for the party and country now is for an orderly transition.”
Ms. West said she would begin collecting the names of colleagues willing to join her in demanding that Mr. Starmer agree to a leadership election in September. The party retains a large majority in the British national Parliament, and a replacement for Mr. Starmer as its leader would also replace him as the nation’s prime minister.
Mr. Starmer’s position has been eroding for months as he has struggled to confront a sagging economy, anger about illegal immigration and the perception that he is weak and indecisive. His decision to appoint Peter Mandelson as ambassador to the United States became a scandal when documents revealed the extent of Mr. Mandelson’s friendship with Jeffrey Epstein, the convicted sex offender.
But the disastrous elections for Labour last week were the final straw for many of his critics. Labour lost more than 1,400 seats on the local councils and was heavily defeated in Wales after decades in power there. Reform U.K. posted victories across Britain, despite winning under 30 percent of the vote in a fractured field of several political parties.
Mr. Starmer took direct aim at Reform’s leader, Mr. Farage, who was one of the loudest campaigners for Brexit more than a decade ago.
“He said it will make us richer. Wrong, it made us poorer,” Mr. Starmer said. “He said it would reduce migration. Wrong. Migration went through the roof. He said it would make us more secure. Wrong again, it made us weaker.”
Over the weekend, Angela Rayner, a former member of Mr. Starmer’s cabinet who is considered one of the lawmakers who might challenge him, said in a statement on Sunday that the party’s agenda must change.
“The prime minister must now meet the moment and set out the change our country needs,” she wrote. “Labour exists to make working people better off. That is not happening fast enough, and it needs to change — now.”
Ms. Rayner did not formally launch a challenge to the prime minister. Neither did Wes Streeting, the current health secretary, who is considered another leading contender to challenge Mr. Starmer’s leadership.
Andy Burnham, the current Labour mayor of Manchester, is seen by many British politicians as the biggest long-term threat to Mr. Starmer. Opinion polls suggest that the mayor is the most popular Labour politician in the country. But he cannot challenge Mr. Starmer until he becomes a member of Parliament, which would require a vacancy that he could run for. He attempted to do that earlier this year, but was blocked by a party committee controlled by Mr. Starmer’s allies. On Monday, the prime minister dodged questions about whether he would block Mr. Burnham again.
“He’s doing a great job as mayor in Manchester,” Mr. Starmer told reporters. “And I actually work really well with Andy.”
He also confronted complaints by Labour candidates who said that voters had told them in recent weeks that they were not voting for the party because of Mr. Starmer.
“I have my doubters who said we couldn’t change this party and make it capable of winning an election. And I proved them wrong,” he said. “I had my doubters who said, ‘You can’t lead us to a general election victory after the loss in 2019. It was so bad, it’s not possible.’ And I proved them wrong. I can prove them wrong again.”
Looming over British politics is the bond market. Yields on government bonds, which move inversely to price, have been rising sharply. Some investors fret that if Mr. Starmer were forced out of office, a more left-wing leader would take charge.
Mr. Starmer’s cautious chancellor, Rachel Reeves, has maintained an ironclad commitment to fiscal rules in order to bring down public debt levels, frustrating some Labour Party members, who said the rules hindered spending on welfare and public services.
On Monday, the yield on benchmark 10-year bonds, or gilts, rose to as high as 5 percent, signaling a concern over political instability and heaping more pressure on the government by increasing debt payments.
Eshe Nelson contributed reporting from London.
