A leading member of a British far-right group has quit after one of his fellow activists was exposed as a former neo-Nazi.

Experts said the UK branch of Generation Identity – a Europe-wide network of white nationalists – could struggle to survive the resignation of Tom Dupré, which comes after the government barred several of its activists from entering Britain.

Mr Dupré, a 23-year-old banker, walked out of the organisation during an annual event where sources said members from 10 countries had “self-defence” classes using plastic knives and other weaponry.

Generation Identity furthers a conspiracy theory that “indigenous Europeans” are being replaced by migration and calls for its members to mount a “Reconquista” of the continent.

It rejects accusations of white supremacism and claims it vets all members carefully, but organiser Tore Rasmussen had been a prominent figure in Norway’s neo-Nazi group Vigrid.

Former members of the neo-Nazi terrorist organisation National Action have also associated themselves with Generation Identity, while an ex-Holocaust denier supported its Defend Europe mission to block refugee rescues in the Mediterranean Sea.

Mr Dupré said he resigned as co-leader of the UK and Ireland branch after being sent a dossier on Mr Rasmussen’s past by The Observer newspaper.

He told The Independent the information was received on Thursday during the group’s so-called “Summer University” in France, when members undergo combat training and indoctrination.

A Generation Identity training camp in summer 2016 (YouTube)

“I essentially resigned after reading it,” Mr Dupré said. “It was very extreme content ... I wasn’t [aware of his past]. I’m not willing to be associated with it in any way.”

Mr Rasmussen has disavowed Vigrid since joining Generation Identity, and admits being charged but then acquitted over the stabbing of an African migrant in the Norwegian city of Stavanger in 2001.

He is among Generation Identity activists to be blocked from entering the UK because their presence is “not conducive to the public good”, following Austrian leader Martin Sellner and his American girlfriend and far-right blogger Brittany Pettibone.

Mr Rasmussen relocated to Dublin as a result of the ban, which came as he attempted to chair the group’s UK conference, and continued his work from Ireland while managing Generation Identity-linked merchandise company Phalanx Europa.

Hours before news of Mr Dupré’s resignation broke, his former co-leader announced that Mr Rasmussen was “leaving the patriotic community in the British Isles to follow personal pursuits in his home country of Norway”.

Benjamin Jones said he had “wiped his hands clean of youthful misjudgements” and praised Mr Rasmussen’s “keen political knowledge and complete integrity”.

Generation Identity members attacked Mr Dupré on Twitter, where the UK branch’s official account claimed he was already due to be “expelled” for violating its code of conduct.

“We’re fine and here to stay,” a tweet claimed.

Mr Dupré, who was fired from his job as a junior banker at Standard Chartered over his role, denied the accusations.

“There were some incidents at the camp and then there was my resigning and they were totally separate,” he added.

“I find Nazism disgusting, I find that kind of violence horrendous as well and I’m just not going anywhere near that ... to some extent the success or failure of groups [like Generation Identity] rests on how well we can keep these people out. I thought we had but clearly not, and that’s why I left.”

But Mr Dupré defended Generation Identity’s core theory of the “great replacement” of white Europeans and added: “I wish them all the best, it’s just not for me anymore.”

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He told The Independent he was going to continue unspecified “activities” with former members of the movement, adding: “What exact form that takes will become clear in the coming months.”

Monitors at Hope Not Hate said the row was not the first time Generation Identity had been linked to “very extreme individuals”.

Simon Murdoch, of Hope Not Hate, said Mr Dupré’s departure was “incredibly bad news” for the group.

“They’ve attempted to portray themselves as moderate, with no Nazi links, and that is a real blow to their image,” he added.

“The question is whether the UK branch will survive at all – there are rumours in the UK far-right that GI’s branch is finished.

“Dupré was clearly most competent, articulate among them and best hope of a leader they had.

“What they’ve got left is a group of rudderless individuals ... and a real dearth of quality activists in the UK.”

Mr Murdoch said the UK had threatened to become an “organising hub” for Generation Identity amid growing links with the British far-right and US alt-right, before the government started cracking down earlier this year.

He estimated that has under 100 active members in the UK, but is “very disciplined” and holds regular stunts including stickering and banner drops.

On the Continent the group is “extremely organised” through an extensive network that runs bars, restaurants, boxing clubs and draws in new followers through its slick online operation.