Rayner said the aim would be to “protect our democracy in the spirit of individuals not being able to overpower and buy their way into democracy at the expense of those people that are at the ballot box”.
She would not be drawn on whether the proposed changes would apply to Delo and Harborne, saying: “I don’t know the individual circumstances of those donors.”
Conservative shadow foreign secretary Tom Tugendhat said it was important to ensure “we do not end up with a sort of Americanisation of politics where money just sort of runs free”.
He said people should be able to support the democratic movements they wished but added that “what we’ve got to be careful about is where different industries, where different financial sources raise questions”.
Liberal Democrat Cabinet Office spokeswoman Lisa Smart said there should be emergency legislation to cap campaign donations and spending.
She said: “No politician should be able to buy the keys to Number 10.”
A Green Party spokesperson said there needed to be “more robust laws” around political donations, adding: “The Labour Party urgently needs to find its spine and support a tight cap on donations from individuals.”
Jenrick said Delo and Harborne – who each gave £36m to the party in two days and now share the record for the largest ever donation given to a UK political party – were “not buying anything, they simply support our agenda”.
Both men had already donated millions of pounds to Reform ahead of the announcement of their latest contributions.
The Times reported in June that Harborne, who has been based in Thailand, had registered to vote in the UK, while Delo had told the Telegraph in April that he was moving back from Hong Kong.
Harborne wrote in the Telegraph on Saturday that Reform was a “start-up party” that lacked “the benefit of hundreds of years of patronage”. Delo had written in the newspaper the day prior that he wanted to enable Reform to put up a “fair fight at the next election.
The £72m from the two is more than the total received by all UK political parties last year.
Delo was pardoned by US President Donald Trump last year over a breach of anti-money laundering laws at his crypto trading platform, BitMex, to which he had pleaded guilty in 2022.
Reform’s fundraising has come under scrutiny in recent months. This includes police announcing an investigation over allegations the party broke foreign funding laws in a broadcast by Channel 4 News last week.
The party’s leader Nigel Farage is also under investigation by the parliamentary standards commissioner over whether he should have declared a £5m gift he received from Harborne ahead of the 2024 election.
Both Reform and Farage have denied any wrongdoing in both instances.