Labour leadership hopefuls with ideas to drag Britain back into Europe might have a fight on their hands as two billionaire Brexit backers vow to put up a fight. Lord Cruddas and Peter Hargreaves, who gave almost £5m to the Brexit campaign, have spoken out after one of the possible Labour leaders, former Health Secretary West Streeting, called the 2016 Brexit vote a "catastrophic mistake".

His words come as Sir Keir Starmer has already mentioned building closer ties with the EU in the face of pressure from the Ukraine and Iran wars and his own volatile personal relations with US President Donald Trump. The third major horse in any leadership race could be exiting Manchester Mayor Andy Burnham who has also spoken fondly of the European Union.

However, Mr Burnham has had to distance himself from Mr Streeting's comments as he has to win a seat in the Makerfield by-election to return to Westminster as an MP. Makerfield, in Greater Manchester, firmly voted leave 10 years ago.

But even if any of the trio end up with the keys to 10 Downing Street, Lord Cruddas and Mr Hargreaves intend to resist any plans for a rekindled EU romance.

Mr Hargreaves, co-founder of the investment platform Hargreaves Lansdown, told the Telegraph: "Fifteen million voted for Brexit whereas only nine million voted for Labour at the general election.

“I wonder what the figure would be if we had a general election today. Would Labour even get four million? They have proved they are totally incompetent and devoid of talent."

Fellow Brexit big beast Lord Cruddas slapped down any Labour intentions saying there was "rhere is no mandate for any UK government to take us back into the EU, without another referendum".

He added it was "political suicide".

Wes Streeting made calls to rejoin the European Union as he called for a “proper contest” to replace Sir Keir and confirmed he would stand if the race is triggered.

Speaking at the Progress think tank’s conference in central London on Saturday, Mr Streeting described Brexit as a “catastrophic mistake”, and broke the ice on a topic which Labour has long avoided revisiting.

Greater Manchester Mayor Andy Burnham has also been probed over his support for returning to the EU as he seeks to stand in the upcoming Makerfield by-election.

Mr Burnham was asked whether he remained in favour of rejoining the EU in an interview with ITV News on Saturday.

He told the broadcaster: “I’ve said in the long term there is a case for that, but I’m not advocating that in this by-election.

“In fact, what I am saying is focus now domestically, Britain has got to focus very much on the here and now and the issues that are affecting people.”