The House of Lords will debate changes to the laws on political donations later on Monday after Reform UK received £72m from two billionaires in 24 hours.
Calls for restrictions are growing after huge donations from Ben Delo and Christopher Harborne, who are both British and have spent time living overseas.
The government is seeking to change the law on donations to UK political parties from British expats, including a £100,000 cap backdated to 25 March.
The leader of one of Labour’s biggest funders, Unite the Union, is among those backing limits on individual donations. In response, Nigel Farage’s party has accused Labour of trying to “rig the system”.
The sheer scale of Reform’s record-breaking donation windfall has prompted an urgent debate across the parties.
On Monday, the bill that would introduce a £100,000 cap on donations from British voters living abroad returns to the House of Lords.
The rules were proposed in a review by former civil servant Philip Rycroft aimed at countering foreign influence in UK politics.
The Labour peer Lord Wills told Radio 4’s Westminster Hour he intended to amend the bill so that donations from those living in the UK could also be capped.
Sharon Graham, the general secretary of Unite, told the BBC a limit on individual donations was necessary.
Her union has donated large sums to Labour in recent years, but she argues that “billionaires splashing out millions” is different from “everyday workers giving 10p a week to a political fund”.
Reform have said “Labour and their union pals know they can’t win an election fairly so now they want to rig the system”.
Questions remain over whether Reform will be able to keep all of the £72m.
Robert Jenrick, the party’s economic spokesman, told the BBC on Sunday the donations were “entirely in line with the law as it is, and as far as we know, the law as it’s going to be in the future”.
The government has also proposed a minimum residency period in which the £100,000 cap would still apply for those who move back to the UK.
This would be in place for the rest of the calendar year and the following calendar year after the person returns.
Housing Secretary Angela Rayner told the BBC’s Sunday with Laura Kuenssberg that the rule changes would apply retrospectively and anyone not complying with them would have “to return that money”.
Rayner added she was not commenting specifically on Delo and Harborne as she did not “understand” their “circumstances”.
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.
BBC News has been told both Delo and Harborne have returned to the UK. Delo is understood to have been back in the country since last year.
The government has previously said it was “determined to tackle” the issue of “mega-donors”, and has established a new taskforce to do this.
