Reform UK leader Nigel Farage has been interviewed by the standards commissioner over an investigation into whether he should have declared a £5 million gift from crypto billionaire Christopher Harborne.

The probe into the alleged failure to register an interest resumed after he won the Clacton by-election.

Mr Farage told the Sunday Times he had been interviewed by Daniel Greenberg, the parliamentary commissioner for standards.

The 30-minute interview took place in the Palace of Westminster last month, he said.

Under Commons rules, new MPs are required to register any gifts worth more than £300 they received in the previous 12 months, except where it “could not be reasonably thought by others” to relate to their political activities.

Mr Farage has said the gift was not political and insisted he has done nothing wrong.

Mr Harborne is one of two crypto-billionaires who donated £72 million to Reform.

The twin £36 million gifts from Ben Delo and Mr Harborne reignited calls for a blanket cap on donations, going further than legislation aimed at restricting donations from overseas sources.

Mr Farage told the Sunday Times he thought the reaction to the donations would be “far worse” but had actually resulted in “some grudging respect… the fact that I managed to pull off a coup of that magnitude, I think people were quite impressed”.

Mr Harborne was based in Thailand, but in June he was reported to have registered to vote in Hampshire.