Nigel Farage has said his £5m gift from a crypto billionaire is “not any of your business”, saying the cash from the British Thai-based businessman Christopher Harborne was “a purely private matter”.

The Reform UK leader also said it was not hypocritical of him to attack Keir Starmer for receiving donations of glasses and suits, because Starmer had been “the leader of the opposition and I was a presenter on GB News”.

Farage, who has called for a general election after Starmer stood down as prime minister, said he was not paid to promote cryptocurrency interests because he already backed changing the law.

“Number one, I wasn’t in politics. Number two, I don’t believe there’s anything in the rules that says I had to declare it. Number three, of course, it is being investigated by standards, so perhaps I’d better not say too much,” he told BBC Radio 4’s Today programme.

“And lastly, even if the UK, even if London became a centre for crypto trading, it would still be a minute part of the global market, and the fact that a marketplace would happen here would not influence the price directly in any way at all.”

Farage said he “wasn’t in politics” in 2024 at the time of the donation, but the BBC interviewer Nick Robinson said Farage had been interviewed for 40 minutes on his podcast about a possible run for parliament. Farage said that was “a very, very difficult decision. I was far from making my mind up.”

Asked if he could return the money to Harborne should he be found to have broken parliamentary rules, Farage said: “I don’t think it’s any of your business, frankly. And if, however, if the standards commissioner decides that it is, we’ll talk about it again.”

Farage has previously described the donation from Harborne as “a reward for campaigning for Brexit for 27 years”.

He was speaking on the 10th anniversary of the Brexit vote, where he had been a key figure in the campaign to leave. Asked if he regretted the vote, he said there had been little appetite from politicians to pursue Brexit benefits.

“I do not regret it at all. I do not regret independence. I do not regret getting back the ability to make our own decisions on regulation, immigration, global trade partners,” he said. “But what has happened is the earthquake that happened 10 years ago today was not accepted by the establishment, many tried to overturn it, and when finally they were pushed into actually getting us to leave the European Union, they then did not implement the wishes of the people.

“That is why we’ve had seven prime ministers in the course of the last 10 years. They haven’t accepted the public vote with good will, and they haven’t implemented it.”

The Cabinet Office minister, Nick Thomas-Symonds, who is leading the government’s renegotiation for closer ties with the EU, said on Tuesday he was disappointed that the EU summit would be rearranged from 22 July because of the Labour leadership change.

But he said he was “backing Andy Burnham to succeed Keir” and there should not be a contest. “I think he has shown, Andy, comprehensively as the mayor of Greater Manchester, that he can carry out that job of delivery,” he told Sky News.

“But secondly, there is the question about leading us into the next general election and defeating Reform and I think Andy Burnham has just shown comprehensively in Makerfield that he can do that, we’ve seen him do it in an election. So I’m backing Andy Burnham and, yes, looking for a swift transition.”