Sharon Graham, the general secretary of Unite, opened the debate, criticising Starmer for removing the allowance while “leaving the super-rich untouched”.
Speaking to loud applause, she told delegates: “Our public services and British industry need investment now.
“It’s no good having sympathy for workers at Grangemouth losing their jobs: they don’t need pity, they need Labour to step up to the plate and not allow a billionaire, who buys a football club as a hobby, to throw these workers on the scrapheap.”
She added: “We are the sixth richest economy in the world; we have the money. Britain needs investment, not austerity mark II. We won’t get any gold badge for shaving peanuts off our debt.
“It’s the wrong decision, and it needs to be reversed.”
Members of Unite and the Communications Workers Union (CWU) who co-sponsored the motion had accused party officials of seeking to silence the unions, as the debate had been moved from Monday to the very end of the gathering on Wednesday after the ministerial speeches had taken place.
Many delegates and union members had also left the conference early in order to attend the funeral of Andy Kerr, a former assistant general secretary of the CWU.
Before the motion was passed, Labour member Maggie Cosin had argued that she did not need the allowance, and hoped the money would go to “the children of this country [who] need it”.
While the conference vote was highly significant, the prime minister could still go ahead and impose the cut to the allowance.
Richard Burgon, who was elected as the Labour MP for Leeds East but was suspended from the party for voting against the government’s plans to keep the two-child benefit cap, said Starmer should respect the conference’s vote.
“There are plenty of people in the leadership of the government and our party who know this particular policy is the wrong choice. It’s not fair. The public doesn’t like it because it’s not fair. It offends the public sense of fair play. But they see a change of position as humiliating.
“We don’t need a kind of macho politics where you never change your position. The prime minister can show fresh leadership by thinking again after this motion.”
Before the motion was passed, the work and pensions secretary, Liz Kendall, told the conference: “Focusing winter fuel payments on the poorest pensioners wasn’t a decision we wanted or expected to make, but when we promised we could be trusted with taxpayers’ money – we meant it.
“And when we were faced with a £22bn black hole, which the Tories left this year, we had to act, because we know what happened when Liz Truss played fast and loose with the public finances. It was working people and pensioners on fixed incomes who paid the highest price.
“We took what I know is a difficult decision, but let me tell you, conference: this Labour government has done more to help the poorest pensioners in the last two months than the Tories did in 14 years.”
A number of cabinet ministers had privately backed the proposal but accepted that the government’s initial explanation of why they had chosen to remove the benefit was not up to scratch.
Simon Francis, coordinator of the End Fuel Poverty Coalition, said: “Labour conference has understood what ministers have failed to acknowledge, that removing the winter fuel payment at short notice and from so many people is wrong.
“If the government persists with the cuts, it will be gambling with pensioners’ ability to keep warm this winter and with that, their health and wellbeing.”
