Brexit backer Arron Banks is facing fresh pressure to explain the source of £8m of funding for the Leave campaign amid claims from a senior MP that he had contradicted his own evidence.

The millionaire businessman is facing a criminal probe over millions of pounds of loans and donations to Leave.EU – a group he co-founded – which has been linked to possible Russian interference in the EU referendum.

Mr Banks sowed confusion when he told the BBC’s Andrew Marr Show on Sunday that all the cash came from a UK-registered company, Rock Services. He insisted he was being targeted by politicians trying to overturn the result of the Brexit vote.

However Damian Collins, the influential Tory chairman of the Culture, Media and Sport Committee, said Mr Banks had previously given evidence to parliament that the company generated no cash of its own and only existed to provide services to his other businesses.

The National Crime Agency launched an investigation into “suspected criminal offences” by Mr Banks and Leave.EU when the elections watchdog said it had reasonable grounds to suspect that Mr Banks was not the true source of the cash.

The Electoral Commission also suspects the money came from Rock Services parent, Rock Holdings, which is registered in the Isle of Man. This would be impermissible under finance rules, the watchdog said.

Mr Collins told the BBC’s Today programme: “Basically Arron Banks said the money came from a holding company that he told the select committee provides services to the other companies he owns.

“What’s not clear is where the money came from to get to that holding company in the first place, because this is a business that in and of itself doesn’t generate cash. The question is where did the money come from?

“It is a discrepancy because what he told us was that Rock Services really just provides services to other companies that he owns – provides cash, makes payments. It doesn’t make any money itself. It’s not selling products and services and generating cash.

“For Rock Services to have money to give to Leave.EU or anyone else, that money has got to have been put in that bank account by another company or another individual.

“If Rock Services made the donation, where did the money come from for Rock Services to do that? That is still not clear. No matter how many times he was asked that question, he didn’t answer it.”

The Conservative MP rejected Mr Banks’ claims that the probe was about trying to stop Brexit, saying it was a matter for parliament, not another referendum.

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He added: “There are two issues here. There is the Brexit process which is ongoing and there is what should be a full and proper investigation into Mr Banks and the source of his funds.”

The row stems from a review of referendum finances by the Electoral Commission, which centres on £2m reported to have been loaned to Better For The Country – which ran Leave.EU – by Mr Banks and his insurance companies. The review also looked at a £6m donation, which he made alone.

Mr Banks and Leave.EU chief executive Liz Bilney deny any wrongdoing.

On Sunday, Mr Banks said: “There was no Russian money and no interference of any type. I just want to be absolutely clear about that.

“The money came from Rock Services, which was a UK limited company. It was generated out of insurance business written in the UK.

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After marching through central London, there will be a rally on stage in Parliament Square, including speeches from Mayor of London Sadiq Khan. 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AFP/Getty A historic moment: thousands march to demand Final Say on Brexit A demonstrator holds a message during a march calling for a People's Vote on the final Brexit deal, in central London on October 20, 2018. - Britons dreading life outside Europe gathered from all corners of the UK to London on Saturday to try to stop their country's looming breakup with the EU. AFP/Getty A historic moment: thousands march to demand Final Say on Brexit Anti-Brexit campaigners take part in the People's Vote March for the Future in London, a march and rally in support of a second EU referendum. PA A historic moment: thousands march to demand Final Say on Brexit Demonstrators take part in the 'People's Vote March for the Future,' in central London, Britain, 20 October 2018. Reports state that the 'March for the Future' is to be led by a column of young people and call for a Peopleâ€™s Vote on the Brexit deal. 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“Contrary to some of the press reports in the FT and other Remain-leaning publications, we insure nearly half a million customers a year – the size of Manchester.

“We turn over £250m of premiums, it’s a sizeable business.”