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Jeremy Corbyn was today warned he must “win or go” as Labour faced the prospect of renewed infighting if he fails to get into No 10.

Despite some polls suggesting the election race is tight, former Labour MPs are braced for Theresa May to be returned to Downing Street with a comfortable majority.

But anger is growing in the party that it could have snatched victory — following blunders in the Conservative campaign — if Mr Corbyn had not been leader.

“Up against the worst performing Tory prime minister in living memory, failing to win the election is an indictment,” said one senior Labour figure. “For Jeremy, it’s win or go.”

Another former MP added: “The annoying thing is if we had got a decent leader, we could have won this election. The problem is he is toxic with some people.”

However, any fresh coup to oust Mr Corbyn is likely to be met with fierce resistance from his supporters, especially if he increases Labour’s share of the vote compared with the 30.2 per cent under Ed Miliband.

Labour centrists are plotting to change leadership election rules back to the electoral college system under which parliamentarians got a third of the votes, local party members a third, and unions a third. Moves to bring in such a reform, ending the one-member, one-vote system, could be launched the party’s autumn conference in Brighton. However, previous attempts to replace Mr Corbyn have failed.

Former shadow business secretary Chuka Umunna refused to talk about the party leader’s future after Thursday’s election but said the “test” for Labour was to win more seats than the Conservatives.

“Jeremy is a Labour person... He’s absolutely right to say we can have a debate about vote share but the main way that Labour makes its values real is by getting more seats than the Tories,” he said.

Mr Umunna, Labour’s candidate in Streatham, believes that the election will be decided by the “fundamentals of competence, leadership and stewardship of the economy”.