The backbench MP now has the support of more than half of those with a vote in the Labour leadership contest, the opinion poll suggests
The Corbyn campaign has continued to gather momentum despite stark warnings from a string of senior party figures that choosing the veteran left-winger would be catastrophic for Labour’s electoral chances, with one grandee comparing him to former Tory leader Iain Duncan Smith.
The YouGov survey for The Times of 1,411 eligible voters in the contest to succeed Ed Miliband at the head of the opposition found Mr Corbyn had nearly doubled his lead in a week to 32 per cent.
It gave him 53 per cent - enough to win without a need to count second preferences - with Andy Burnham losing five points to 21 per cent, Yvette Cooper slipping two to 18 per cent and Liz Kendall down three on 8 per cent.
Tony Blair’s former spin doctor Alastair Campbell has urged Labour supporters to sign up to vote for “anyone but Corbyn” to help the party “stop itself driving over a cliff”.
Lord Soley, a former chairman of the Parliamentary Labour Party, compared the prospect of a victory for Mr Corbyn to Mr Duncan Smith’s disastrous leadership of the Conservatives.
He said: “The country did not see Ed Miliband as a potential prime minister and they won’t see Jeremy Corbyn as a potential prime minister either.”
Serial rebel Mr Corbyn had been accepted as a “maverick” within the party but discipline was needed in parliament, Lord Soley said.
“In his many years as an MP Jeremy put his individual judgment before the collective judgment of the parliamentary party.
“As a party we accepted that because we always accepted that there is a place for mavericks but if the maverick becomes the leader who called for individual judgment to be used over and above collective decision making then the message is clear.
“The party in Parliament becomes a collection of individuals - not a political party. That might be exciting in an party election campaign but it is a joy for the Tory party as it cements their position in power.
“It might focus minds before this important vote if we recall how delighted we were when Iain Duncan Smith became leader of the Tory party. We wanted him to stay. We should not fall into the same careless way of thinking.”
Former Cabinet minister Stephen Timms, who backed Ms Kendall, claimed a win for Mr Corbyn would be “damaging”.
Mr Timms told BBC Radio 4’s Today programme: “If it’s accepted, as I believe, that it was economic credibility that was our big problem in the general election, I don’t think a victory for Jeremy Corbyn would help us to overcome that.”
He added the consequence of this would be a “damaging one for Labour and for the country”, noting he believed it would be “potentially long-term”.
Bookmakers have slashed the odds on a Corbyn win, with the former outsider now firmly installed as favourite.
William Hill now has Mr Corbyn at 1/2, after he had started out as a 200/1 shot, and the bookmaker faces a “potential five-figure loss” if he succeeds.
Spokesman Graham Sharpe said it looked as though they had “completely under-estimated Jeremy Corbyn’s chances”, adding: “We can recall no other example of a 200/1 chance becoming an odds-on favourite in a political betting market in our 50-plus year history of political betting.”
YouGov president Peter Kellner said he “would personally be astonished if Corbyn does not end up as Labour’s leader” despite voting not starting until Friday and the result not being declared until September 12.