LONDON — Britain’s left-wing opposition leader said Wednesday that the political center ground has shifted and his socialist ideas are “now the political mainstream.”

Wrapping up the Labour Party’s annual conference, Jeremy Corbyn said the party espoused “a new common sense about the direction our country should take,” and had become Britain’s government-in-waiting as the Conservatives were consumed by infighting.

Labour stunned pundits and pollsters in June’s snap election by reducing Prime Minister Theresa May’s Conservatives to a minority administration. The party ran on policies widely derided as expensive and old-fashioned, such as nationalizing railways and public utilities and scrapping university fees.

But they struck a chord with many voters weary after seven years of spending cuts by the Conservative government. Although Labour lost the election, it gained several dozen parliamentary seats, and its membership has grown to almost 600,000 since Corbyn was elected leader in 2015.

Many Labour lawmakers still worry that Corbyn’s socialism is a turn-off to centrist voters. But, to a boisterous reception from delegates, the leader argued that “we are now the political mainstream.”

“Today’s center ground is certainly not where it was 20 or 30 years ago,” Corbyn said. “A new consensus is emerging from the great economic crash and the years of austerity, when people started to find political voice for their hopes for something different and better.”

Labour has lost three successive elections since 2010, but its four-day conference in the seaside city of Brighton was the most optimistic in years.

Corbyn made eye-catching promises including a pay raise for public servants and constraints on private landlords and developers that he said had contributed to “social cleansing” in London.

Corbyn cited June’s fire at public housing block Grenfell Tower, which killed some 80 people, as “a damning indictment of a whole outlook … which has contempt for working-class communities.”

And he derided May’s attempts at global influence, especially her visit to President Donald Trump in Washington soon after his inauguration.

“We must be a candid friend to the United States, now more than ever,” Corbyn said, calling Trump’s bellicose speech to the United Nations General Assembly last week “deeply disturbing.”

“If the special relationship means anything, it must mean that we can say to Washington, that is the wrong way,” he said.

Despite the party’s optimistic mood, Labour remains divided over one of the biggest issues facing Britain: Brexit.

Some members and lawmakers want to push to keep Britain inside the bloc’s single market after Brexit, but Corbyn and his allies are cool to that idea.

Corbyn said Labour would respect voters’ decision to leave the EU, guarantee the rights of 3 million EU citizens living in Britain and “build a new and progressive relationship with Europe” — though the nature of that relationship remains undefined.

Trade unions welcomed Corbyn’s speech, but business groups expressed concern.

Adam Marshall, director-general of the British Chambers of Commerce, said the speech “will have done little to reassure companies already worried about widespread state intervention, nationalization and the radical increases in taxes and costs they could face under a future Labour government.”