The House of Lords is due to debate proposed changes to UK political donation rules after Reform UK received £72m from two wealthy donors in a 24-hour period.

The government wants to introduce a £100,000 cap on donations from British voters living abroad and apply it retrospectively from 25 March. It has also proposed a residency rule covering the rest of the calendar year and the following year when a donor moves back to the UK.

The proposals follow donations of £36m each from Ben Delo and Christopher Harborne. Both donors are British and have spent time living overseas. The government says the changes are intended to address concerns about foreign influence and large donations, following a review by former civil servant Philip Rycroft.

Reform deputy leader Richard Tice said the party had complied with the law and accused Labour of attempting to change the rules retrospectively to disadvantage a political rival. He argued the donations would help Reform compete with other parties, including Labour, which receives financial support from trade unions.

Paul Nowak, general secretary of the Trades Union Congress, rejected that comparison. He said contributions from workers through union political funds were not equivalent to donations from billionaires and called for a broader discussion about cleaning up politics.

Labour peer Lord Wills said he planned to seek an amendment that would also cap donations from people living in the UK. Unite general secretary Sharon Graham backed a limit on individual donations, saying large payments from billionaires differed from small contributions made by ordinary union members.

Questions remain over whether Reform will be able to retain the full £72m if the proposed rules are enacted. Housing Secretary Angela Rayner said donations that did not comply would have to be returned, while stressing that she was not commenting specifically on Delo or Harborne because she did not know their circumstances.

Reform economic spokesman Robert Jenrick said the donations complied with the law as it currently stood and, as far as the party knew, with the law that would apply in future. The government has also established a taskforce on large political donors.