Robert Jenrick, Reform UK’s economic spokesman, said on Sunday the donations were โ€œentirely in line with the law as it is, and as far as we know, the law as itโ€™s going to be in the futureโ€.

But Deputy Prime Minister Angela Rayner appeared to suggest they could be covered by the cap on overseas donors, which will be backdated to March 25.

The rules, which limit donations from overseas electors to ยฃ100,000 per year, were proposed in a review by former civil servant Philip Rycroft aimed at countering foreign influence in UK politics.

Ms Rayner told the BBC: โ€œWith the retrospective action, anyone thatโ€™s received donations that donโ€™t comply with what was in the Rycroft review, what legislation is currently going through Parliament, would have 60 days to return that money.

โ€œThat is not for those individuals, let me be really clear, I do not understand those individual circumstances, but that the retrospective action will apply from March 25.โ€