BRIGHTON, England — After days of internal discord, Britain’s main opposition leader, Keir Starmer, ended the Labour Party’s annual conference on Wednesday with a series of pledges intended to shift his party to the political center and deliver a clear break with the legacy of his left-wing predecessor, Jeremy Corbyn.
Speaking for 90 minutes, and sometimes interrupted by heckling, Mr. Starmer promised a “serious program for government” with more investment in health care, mental health provision, education and the environment — while stressing his patriotism and toughness on crime.
The speech marked a rupture with the leadership of Mr. Corbyn — a veteran socialist sometimes compared to Senator Bernie Sanders, Democrat of Vermont. Mr. Corbyn enjoyed some electoral success in 2017, but then in 2019 led the Labour Party to its worst defeat since the 1930s.
It was the first time Mr. Starmer had addressed the annual conference in person since taking over the leadership last year, and he sought to use the occasion to present the party as a credible alternative to the Conservative Party, led by Prime Minister Boris Johnson.
Mr. Starmer seized on a shortage of truck drivers that has recently unnerved the country with the resulting long lines at gas stations and empty supermarket shelves. He accused Mr. Johnson of “ignoring the problem, blaming someone else, then coming up with a half-baked solution.” The prime minister was not a bad person but a “trivial” one, Mr. Starmer said — “a showman with nothing left to show.”
While that line brought cheers, there was also persistent heckling from critics after a conference dominated by infighting between the leadership and the left of the party.
Paradoxically, that might have helped Mr. Starmer, a former chief prosecutor not renowned for his oratory, by injecting drama into an extremely long speech. More important, it underscored one of his main messages: that the party must adopt a centrist approach to win back voters and challenge the Conservatives.
Mr. Starmer also seemed prepared for interruptions, shooting back at one point that there was a choice between “shouting slogans or changing lives.”
His policy promises included a tougher sentences for rapists, stalkers and domestic abusers; more focus on teaching digital skills in schools; better resources for health care; and a spending target for research and development of 3 percent of gross domestic product.
But Mr. Starmer also underscored a more business-friendly stance by arguing that “without a strong economy, we cannot pay for the good society.”
Mr. Corbyn’s remaining allies are not happy with Mr. Starmer’s desire to leave them behind, and on Monday, one of them, Andy McDonald, resigned from the Labour leader’s top team.
There have also been tensions with Mr. Starmer’s deputy, Angela Rayner, who made her own news early in the conference when she referred to Mr. Johnson and Conservative ministers as “scum” and refused to apologize for her language. Other internal rivals of Mr. Starmer’s have used the occasion to raise their profile; they include the mayor of Manchester, Andy Burnham, who did not speak from the main stage but was a frequent presence at the conference’s fringe events.
Yet the main question hanging over Mr. Starmer’s leadership is whether he has the charisma and vision to appeal to voters, and the political savvy to exploit the failings of Mr. Johnson, whose party remains strong in opinion polls despite the government’s missteps.
Labour has a steep electoral challenge if it is to win the next general election, which must take place by 2024 but is likely to be called a year earlier. Conservatives hold a comfortable 80-seat majority in Parliament.
So Mr. Starmer has tried to use the conference to reposition his party, calculating that it’s essential for centrist voters to believe that Labour has turned its back on the Corbyn era.
One of his conflicts with the left came over a series of important internal rule changes, which reduce the prospect of anyone with Mr. Corbyn’s ideological views again winning the party leadership. The new rules also limit the power of local activists to oust sitting Labour lawmakers, some of whom had been targeted by the left.
Some left-wingers feel betrayed because Mr. Starmer won his job last year on a promise to unite the party, but he has since tried to court traditional Labour voters in the north and middle of the country who abandoned the party in 2019.
He has also sought to move the party past the years of damaging wrangling over anti-Semitism within its ranks. Mr. Corbyn remains suspended from Labour’s parliamentary group because of his deflection of blame for how the party handled the problem.
There, Mr. Starmer scored a success when Louise Ellman, a former Labour lawmaker who quit over the anti-Semitism issue, returned to the party after a new disciplinary system was adopted.
In Brighton, Mr. Corbyn was received warmly by activists at speaking events affiliated with the conference. In defiance of Mr. Starmer, the conference also voted in favor of nationalizing the energy industry and of a national minimum wage of £15, a much higher figure thanMr. Starmer is committed to.
But the votes are nonbinding — underscoring the fact that, along with Mr. Corbyn himself, the left is back on the party’s political fringes.