Conservative Party leader Kemi Badenoch last month said the UK should not pay compensation for “a crime we helped eradicate and still fight today”.
Reform’s policy proposal comes a fortnight after the United Nations General Assembly backed a resolution declaring the transatlantic slave trade “the gravest crime against humanity”.
The resolution also emphasised that reparation claims “represent a concrete step towards remedying historical wrongs against Africans and people of African descent”.
It was adopted by 123 votes to three, with the UK among the countries that abstained.
Reform named several countries in the Caribbean and Africa as those it considers to be making demands for reparations, and said its policy proposal would put them “on notice”.
The party said it would consider the establishment of national reparations committees or task forces, tabling motions at the UN, making high court claims and official declarations to be among actions it regards as a formal demand.
Those named included Barbados, Jamaica, Nigeria and the UN resolution’s proposer Ghana.
Reform said “from this point” should any country formally demand reparations from Britain, then a future Reform government would respond “by immediately halting the issuance of new visas to their nationals”.
Zia Yusuf, Reform’s home affairs spokesman, said countries seeking reparations “ignore the fact that Britain made huge sacrifices to be the first major power to outlaw slavery and enforce this prohibition”.