Nigel Farage has repeatedly refused to answer questions about a personal gift of £5m he received from the billionaire Christopher Harborne, as the Reform UK leader sought on Friday to focus attention on the party’s election gains.

Farage was clearly irritated when asked on a number of occasions on Friday about the money, which the Guardian revealed he had received shortly before announcing he would stand in the 2024 general election and which was not declared.

“Yeah yeah, well we’ll talk about that any other time that you’d like,” Farage said, when asked as he celebrated Reform’s capture of its first London council, in Havering.

The Electoral Commission said last week that it was considering whether to investigate the undisclosed £5m gift after the Conservatives urged the watchdog to initiate an investigation. The party has also written to the parliamentary commissioner, citing rules that require MPs to declare any “personal benefit” they have received in the 12 months before taking office, and to do so within a month of being elected.

The gift from Harborne, a Thailand-based crypto billionaire who has become a big donor to Reform, fell within that period. Some personal gifts are exempt from the reporting rules if they “could not reasonably be thought by others to be related to membership of the house or to the member’s parliamentary or political activities”, according to the code of conduct and rules for MPs.

The rules add: “Both the possible motive of the giver and the use to which the gift is to be put should be considered. If there is any doubt, the benefit should be registered.”

In an interview with LBC Radio on Friday, Farage declined to discuss the money when the matter was raised, telling the broadcaster Nick Ferrari: “If you want to have a discussion with me at some point about illegally obtained information that should not be in the public domain we can talk about it.”

Other senior figures in Farage’s party also came under pressure on Friday and on election night over the gift, which underlines the pivotal role Harborne has in British politics.

Last year, he donated £9m to Reform UK – the largest ever single donation by a living person to a British political party. In total, Harborne gave £12m to the party in 2025.

“It hasn’t come up on the doorstep. It is a Westminster bubble story,” Reform’s chair, David Bull, claimed on BBC News.

He went on to claim that no voters had mentioned it over the past year when he had met tens of thousands of voters, before the Conservative MP Richard Holden pointed out that the existence of the gift had only come to light in the last 10 days.

“Our understanding was that he [Farage] didn’t have to declare it, but if there is an issue IPSA [Independent Parliamentary Standards Authority] can investigate it and that is the end of that as far as I am concerned,” Bull said.

He was also challenged by the deputy prime minister, David Lammy, after repeating a claim that the £5m had been for Farage’s security.

“Five million for security ... what is it? Brink’s-Mat?” said Lammy, referring to one of the largest robberies in British history, in 1983.