Nigel Farage’s Reform UK 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 detectives to investigate the claims which have plunged Reform into its biggest crisis.

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.

Party chairman Lee Anderson told Times Radio: “The two people involved-they've gone. They've left the building. That's the right thing to do.

“And Nigel's going nowhere.”

He added: “I'm confident that we've not broken any laws at all.”

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 today that his top team haven’t broken the law and secretly plotted to undermine our democracy.

“It’s not just Farage’s secret £5 million ‘gift’. Time and again he and his mates think the rules don’t apply to them. The sleaze and scandal now engulfing him and his party isn’t going away – it’s getting worse.”

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.”

Green Party leader Zack Polanski said: "These very serious claims should be fully investigated by the Electoral Commission and the police.

"There are millions of reasons why Nigel Farage is happy to take money from billionaires, climate science deniers and secret foreign backers, and not one of them is because he has any interest in improving people's lives.”

Liberal Democrat Cabinet Office spokeswoman Lisa Smart added: “Farage has always behaved as though the rules apply to everyone but him. These new allegations against Reform look like the latest example and must be dealt with swiftly by the authorities.”

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.”

The allegations threaten to derail Reform’s conference taking place at the Birmingham NEC on Friday and Saturday, which has been billed as setting out the party’s plans for the first 100 days of its possible government.

Mr Farage is set to give a keynote speech in which he will vow to make Parliament sit seven days a week to “fix” Britain if his party wins the next election.

He is expected to say he would declare a “national emergency” on the first day of government, introducing a flood of legislation and doing “anything and everything” to deliver the party’s policies.

In the first of his two speeches at the conference, he will say: “Within days of winning the general election, we will introduce dozens of Bills and force Parliament to sit all through summer for seven days a week to pass them.

“Britain is in serious trouble. We don’t have time to wait around to fix it.”