Jeremy Corbyn is under pressure to use a speech next week to begin a new push to turn around his and his party’s “devastating” poll ratings.

Labour MPs say they were promised a relaunch this month and that was before the most recent poll showed just 14 per cent of people now see the party’s leader as a potential Prime Minister.

The YouGov survey gave Theresa May’s Conservatives a 13 point lead over Mr Corbyn’s party, just days after his close ally and Unite the union boss Len McCluskey indicated the leader may step aside if ratings are “still awful” in 2019.

Labour sources confirmed that Mr Corbyn will give a speech on Tuesday after MPs return from their Christmas break.

While the content is unconfirmed, the party’s MPs say they were promised a relaunch in January, while Labour election coordinator Jon Trickett said in December that work was going on to “frame an argument about Britain”.

YouGov’s most recent survey, conducted between 3 and 4 January, asked people which of the party leaders would make the best Prime Minister, with just 14 per cent opting for Mr Corbyn, while 47 per cent backed Theresa May and 39 per cent did not know.

Mr Corbyn’s rating was a fall of two points from the previous survey and a further decline from a high of 21 per cent in August last year.

Labour’s Bermondsey and Old Southwark MP Neil Coyle told The Independent: “Team Corbyn have said they will announce a new strategy this month, and that fits with Jeremy’s closest allies calling for him to do better. Diane Abbott, Ken Livingstone and Len McCluskey have all acknowledged he must do better.

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“What I find disturbing though is the number of voters who already appear to have made their mind up about Jeremy. Every leader of our party or opposition leader, Cameron, Blair, whoever, there was always a lot who hadn’t made their mind up.

“Sadly with Jeremy too many have made their minds up too soon. Only he can act now to turn around these devastating ratings.”

The YouGov poll put the Conservatives on 39 per cent again, Labour two points up on 26 per cent and the Lib Dems two points down on 10 per cent. Ukip were unchanged on 14 per cent.

A spokesperson for Mr Corbyn said: “Rebuilding Labour support after its fragmentation at the 2015 election was always going to be a challenge.

“But Labour under Jeremy Corbyn will be taking its case to every part of Britain in the coming months with a radical policy platform, offering the only genuine alternative to a failed parliament political establishment and the fake anti-elitists of the hard right.”

Mr McCluskey, whose union gives millions of pounds a year to Labour, used an interview just after the New Year to raise the prospect of Mr Corbyn throwing the towel in.

The Unite general secretary said: “Let’s suppose we are not having a snap election. It buys into this question of what happens if we get to 2019 and opinion polls are still awful.

“The truth is everybody would examine that situation, including Jeremy Corbyn and John McDonnell.”

He added that the pair are “not egomaniacs, they are not desperate to cling on to power for power’s sake.”