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, Reform UK’s deputy leader Richard Tice said the proposed change shows Labour was “terrified” of the party.

“We believe that we’ve done everything in complete accordance with the laws,” he told BBC Breakfast.

He accused Labour of trying to “retrospectively introduce legislation in order to significantly disadvantage another political party”.

Tice said the party’s donations would enable it to “get on a level playing field” with other parties, likened it to Labour receiving donations from trade unions, and that “competition is a good thing”.

Earlier, the general secretary of the Trades Union Congress (TUC) Paul Nowak pushed back on suggestions that Reform’s donations was the same as trade unions funding Labour and influencing policy, saying “trade union money is the cleanest, most transparent money in British politics”.

Speaking to the BBC Radio 4 Today programme ahead of the first full day of the TUC conference, he said: “Every decision that unions take about political funding, members decide, it’s all in the open.

“Any conversation I ever have with a minister or a politician, everybody knows what I’m talking about, nobody knows what goes on behind closed doors with Christopher Harborne, Ben Delo and Nigel Farage.”

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.