Lord Mandelson has reignited Labour’s internal wars by saying he is working “every single day” to bring down Jeremy Corbyn.

In a stinging attack, the former cabinet minister accused the Labour leader of living in “a parallel universe” – arguing the party is on “life support” and must be rescued.

The intervention came as a new ICM/Guardian opinion poll underlined Labour’s woes by giving the Tories an 18-point lead over Labour.

Speaking to The Jewish Chronicle, Lord Mandelson said: “I work every single day to bring forward the end of [Mr Corbyn's] tenure in office.

“Every day I try to do something to rescue the Labour Party from his leadership.”

The peer, one of the architects of New Labour and Tony Blair’s key ally, added: “The problem with Jeremy is not that he’s a nasty man. It’s as if he's in a parallel universe.

“He’ll gravitate to whatever revolt, insurrection, every protest movement in sight.

“He’s been like this for 35 years. He was not a frequent supporter of the last Labour government – he voted against it 500 times!”

But Lord Mandelson ruled out leaving Labour as a lost cause, insisting: “Why do you want to walk away and pass it to Jeremy Corbyn? I resent it.”

Asked about Labour support among the Jewish community falling to 8 per cent, he joked: “That high!”

The comments, made at a Jewish Chronicle event in London on Monday evening, drew a furious response from a Labour source, who told HuffPost UK: “The idea of Jeremy Corbyn being Prime Minister and implementing policies that actually benefit the people terrifies the establishment.

“So it is no surprise Peter Mandelson has found time in his busy schedule of spending time on oligarchs’ yachts to attempt to undermine him.”

The jibe was a reference to an incident in 2008, when Lord Mandelson joined George Osborne on a yacht belonging to Russian tycoon Oleg Deripaska, as a guest of financier Nathaniel Rothschild.

As the peer was speaking, Mr Corbyn was facing fresh questions about his leadership at the weekly meeting of the Parliamentary Labour Party in the Commons.

The leader admitted that the Copeland and Stoke-on-Trent Central by-elections this Thursday are “on a knife-edge” – although they are both Labour-held seats.

One Labour backbencher told him that the “main problem on the doorstep ... is Jeremy Corbyn,” it was reported.

But, asked to explain the dire poll ratings, Mr Corbyn was said to have referred to “problems we have had in the media”, adding: “We do a lot better on social media”.

It was Lord Mandelson’s second big intervention in just three days, after he told The Independent that the British public must be given the right to “pass judgement” on Theresa May’s Brexit deal.