Embattled Nigel Farage maintained that Reform UK had not accepted “dodgy money” as it was plunged into its biggest crisis ever.
Reform is facing a police investigation over allegations the party breached political donation rules by having polling paid for by an overseas company.
Labour, the Liberal Democrats and the Green Party called for Scotland Yard to investigate the claims.
The spiralling storm was threatening to overshadow the party’s annual conference in Birmingham.
As Reform chiefs sought to get a grip on the situation, two top officials - Mr Farage’s press chief Dan Jukes and head of policy James Orr - stepped down from their roles pending the outcome of an investigation by the party into the broadcast by Channel 4 News alleging it breached political donation rules.
Responding to the swirl of accusations, Mr Farage told LBC Radio: “The party has broken no laws. The party has not taken any dodgy money or anything like that whatsoever.”
Earlier, Reform chairman Lee Anderson stressed that Mr Farage was not about to resign.
He told Times Radio: “The two people involved - they've gone..and Nigel's going nowhere.”
Mr Farage, Reform and Mr Jukes deny any wrongdoing.
The Reform leader also dismissed suggestions that the party had previously taken disguised foreign donations as “loose pub talk” that “simply were not true”.
Mr Farage’s party took funding from a “US firm” for three polls it commissioned earlier this year costing £32,500, Channel 4 News reported on Thursday night.
The purported donors were actually undercover reporters from investigative group Verbatim posing as an American financier and his UK-based son.
Foreign companies are not allowed to provide funding for UK parties, including for payments for studies and research, under electoral law.
The polls, by JL Partners, were covered in national newspapers but journalists were not told that they had been funded by foreign donors acting on behalf of Reform.
A Met Police spokesman said: "We’re aware of media reporting involving political party donations and an alleged breach of the Political Parties, Elections and Referendums Act 2000 relating to polling. We will assess this matter and any information provided to us.”
The revelations by Channel 4 and Verbatim come amid ongoing scrutiny of the funding of both Mr Farage and his party.
The Reform leader faces a parliamentary investigation into whether he should have declared a £5 million gift from Thailand-based crypto-billionaire Christopher Harborne given shortly before he was first elected to the Commons in 2024.
Reform denies any wrongdoing.
But Labour Party chairwoman Bridget Phillipson said: “This scandal goes right to the top of Reform UK.
“Nigel Farage needs to urgently prove that his top team haven’t broken the law and secretly plotted to undermine our democracy.”
In a letter to Met Commissioner Sir Mark Rowley she stressed: “The allegations are unusually serious because they do not concern an apparent administrative error or uncertainty over the permissibility of a donor.
“The published material describes arrangements which appear to have been designed to conceal the source of political funding...
“We therefore believe there is a proper basis for a police investigation.”
Reform said it had “been the target of a hoax perpetuated by foreign-funded, climate change activists posing as would-be party donors”, adding: “Reform UK has a robust vetting process for prospective donors approved by the Electoral Commission.”
