Nigel Farage on Sunday claimed Reform would have returned a £500,000 donation at the centre of a funding row.
Police are facing fresh calls to investigate claims that Mr Farage was willing to accept the donation despite being warned the money was coming from the United States in an apparent breach of a ban on foreign donations.
Undercover footage broadcast by Channel 4 last week showed the Reform UK leader thanking two fake donors as it was explained to him that a man posing as an American businessman would donate the money via his UK-based son.
Mr Farage told the BBC's Sunday with Laura Kuenssberg: 'People send us money, we send money back all the time if it's not compliant. And if any money had come through this route, it would have been sent straight back.'
Mr Farage was forced to sack top aide Dan Jukes and policy chief James Orr on Friday after they were recorded apparently discussing ways to get round electoral law.
Mr Farage insisted the men were not authorised to deal with donations.
The Reform UK leader claimed he had not been paying attention when the plan was set out over a lunch of champagne and oysters in Clacton, where he was battling to secure his re-election at a by-election triggered over another funding row this summer.
He said: 'I am not a compliance officer. I turn up, I frankly wasn't even listening.'
Nigel Farage on stage after delivering his closing speech on the third day of Reform UK Annual Conference
Mr Farage sings the national anthem with other Reform UK members including Richard Tice, Zia Yusuf and Lee Anderson
Police and the Electoral Commission are assessing potential evidence from the reporting by the US group Verbatim Investigations.
Business Secretary Jonathan Reynolds told Times Radio: 'Any political party that aspires to power and wants to win the confidence of the British people must be willing to abide by British laws and rules. That is the minimum we should expect.'
Shadow Chancellor Andrew Griffith said: 'As a leader, you cannot absolve yourself on matters that are so important.'
But Mr Farage said: 'This has been a deliberate attempt to do this to us. I don't believe we have any guilt at all, none whatsoever.'
Meanwhile, Robert Jenrick yesterday reacted to footage of a protester being dragged by her hair at Reform's conference in Birmingham by saying 'boohoo'.
A video showed audience members pulling the protester's hair, with a man then hitting her with a walking stick.
Asked about the incident on Sky News's Sunday Morning programme, Mr Jenrick said: 'Oh boohoo.'
'We're now in a country where somebody who is – whatever she is – a far-Left protester, goes into a party conference, tries to wreck the leader's speech, and cries foul if a pensioner knocks her over the head with their Zimmer frame, I mean, come on, get a life.'
West Midlands Police has asked the protester to come forward in light of the footage.
Reform UK's home affairs spokesman Zia Yusuf condemned members who pulled the hair of the heckler.
Chairman Lee Anderson said the party would be having a 'whip round' for an audience member who was seen hitting the protester with a walking stick.