The TV grilling of Brexit backer Arron Banks has exposed a "discrepancy" in his account of how he sourced £8 million of funding to the Leave campaign, a senior MP has said.
Mr Banks has insisted there was "no Russian money and no interference" after a criminal probe was launched into the source of the money.
The businessman and co-founder of the Leave.EU campaign told BBC One's Andrew Marr Show that all the cash came from a UK-registered company, and repeated claims that he was being targeted by Remain-supporting politicians.
But Damian Collins, chairman of the House of Commons Culture, Media and Sport Committee, said Mr Banks had previously given evidence that the company existed to provide services to his other enterprises, and generated no cash of its own.
A National Crime Agency (NCA) probe has been launched into "suspected criminal offences" after the Electoral Commission said it had reasonable grounds to suspect that Mr Banks was not the true source of the cash.
The elections watchdog also said that loans involved a company – Rock Holdings – based on the Isle of Man, which was impermissible under finance rules.
Mr Collins told BBC Radio 4's Today programme that Mr Banks' TV appearance had gone "not very far" in establishing the facts.
"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," said the Conservative MP.
"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."
Mr Collins rejected suggestions that the UK's departure from the European Union should be put on hold while the investigation into Mr Banks and Leave.EU is carried out.
Questions over the validity of the referendum result could be raised only if misconduct was "proven to be true as a consequence of the investigation", he said.
The "unprecedented" involvement of the NCA in the case was an important step because the agency was able to examine all financial records of Mr Banks's businesses, including in areas outside UK jurisdiction such as the Isle of Man, said Mr Collins.
"I want this to be done as quickly as possible," he said. "But this isn't a question of what should be done about the referendum. Ultimately that is a matter for Parliament.
"It's important that the investigation goes ahead as quickly as possible and that Arron Banks is investigated. There's an argument he uses which is to say this is all politically motivated, this is not a proper investigation, it's about trying to delay Brexit.
"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 Electoral Commission's review of referendum finances focused on £2 million reported to have been loaned to Better For The Country by Mr Banks and his insurance companies and a £6 million donation which he made alone.
Mr Banks and Leave.EU chief executive Liz Bilney deny any wrongdoing.