LIVERPOOL — Jeremy Corbyn, leader of Britain’s opposition Labour Party, doubled down Wednesday on his platform, promising to sweep away “greed is good” capitalism and expand the state’s role in the economy as he closed an annual conference dominated by divisions over European Union withdrawal.
Outlining a “radical plan to rebuild and transform” Britain, Mr. Corbyn underscored his ambition to shift economic policy leftward — a position that he described as the “new common sense of our time” after a decade of stagnating wages and squeezed living standards.
In a speech intended to present him as a prime minister in waiting, Mr. Corbyn said that it would be a “national disaster” if Britain quit the European Union without a deal. If Prime Minister Theresa May cannot negotiate a satisfactory withdrawal agreement, he said, she should “make way for a party that can and will.”
Mr. Corbyn had harsh words for familiar adversaries in the British news media, which is mainly hostile to him and which, he said, enjoys the “freedom to spread lies and half-truths.”
As for President Trump, Mr. Corbyn derided “America First posturing” and the decisions to pull out of the Paris climate accord and the Iran nuclear deal and to move the United States Embassy in Israel to Jerusalem. “He is turning his back on international cooperation and even international law,” Mr. Corbyn said.
In the domestic sphere, Mr. Corbyn proposed to expand free child care and create 400,000 jobs in clean-energy technologies.
But the hot topic at the Labour Party conference in Liverpool was whether to offer a referendum to allow Britons to rethink their decision on European Union withdrawal, known as Brexit. The debate mirrored a broader divide in British society as concerns grow that the exit will be economically damaging, and as supporters and opponents of withdrawal fail to find common ground about the way ahead.
In Liverpool, a spirited discussion ultimately produced a fudge: The conference agreed on a motion that keeps all options open — including another referendum — but placed a premium on the push for a general election.
Mr. Corbyn, never a fan of the European Union, is hoping that the gathering crisis over Brexit will give him the opportunity to become prime minister well before the next scheduled national vote, in 2022. By then he would be nearly 73. But there is little chance of that happening unless Mrs. May opts for an election to seek approval for her much-criticized Brexit strategy.
Support for Mr. Corbyn remains high among his party members and from trade unions delighted at the party’s shift to the left. But the conference lacked some of the euphoria of last year’s gathering, which followed a general election in which Mr. Corbyn performed better than critics had expected, depriving Mrs. May of her parliamentary majority.
Some of the shine has been removed by months of feuding over the party’s approach to anti-Semitism, a dispute needlessly prolonged by Mr. Corbyn, who ultimately retreated on the issue, but not before damage had been done to Labour’s reputation.
On Wednesday, Mr. Corbyn acknowledged that the summer had been “tough” and that the dispute had caused “hurt and anxiety” to the Jewish community. He promised that his party would “always be implacable campaigners against anti-Semitism and racism in all its forms.”
Worryingly for party bosses, despite months of constant crisis within the government over Brexit, Labour still lags in most opinion surveys.
A big majority of Labour members favor another referendum, according to pollsters. But Brexit has been difficult for the party because the issue splits its base. While many of its voters in big cities wanted to remain in the bloc, many others in working-class communities left behind by globalization opted to leave.
Not only are senior Labour figures divided on whether to keep open the option of a popular vote on any Brexit deal the government negotiates, they are also split on whether to include in a vote the option to remain in the bloc.
On Tuesday, Keir Starmer, the party’s Brexit spokesman, received resounding applause from the conference hall when he told party members that no one was taking the “remain” option off the table, though more Eurosceptic figures had tried to do so.
Business leaders fret about Mr. Corbyn’s left-wing agenda, which includes a plan to force large companies to surrender 10 percent of their shares to funds managed for their workers. But they are growing more alarmed daily by the prospect of Britain leaving the European Union in March without any deal.
At a meeting held on the fringes of the conference, Carolyn Fairbairn, the director general of the Confederation of British Industry, said she had been “really careful about language” when discussing Brexit. She said she had “only started using the word ‘catastrophe’ in the last few months.”
But at the same meeting, Caroline Flint, a lawmaker who had argued for Britain to remain but who now wants to proceed with Brexit, warned that any move to stop it could inflame voters and lead to a resurgence of the far right.