The dissenting judge (in three parts of the judgment), Judge Edward Korman, stated that “[the] lawsuit [is] an insult to the post-apartheid, black-majority government of a free people”.

He goes on to say that a decision to hear these cases would “reflect[] the worst sort of ‘judicial imperialism’ … [and] send the message that the United States does not respect the ability of South African society to administer justice by implying that US courts are better placed to judge the pace and degree of South Africa’s national reconciliation”.

The US government has said the litigation would cause "significant tension between the United States and South Africa".

Citi is considering its legal alternatives in the case, said Donna Oosthuyse, the global banking giant's chief operating officer in South Africa.

She said the company had contributed more than R25m since 1999 in programmes focused on education, literacy and community development for historically disadvantaged South Africans.

She said the projects were not reparations, but part of a business model that Citi practices everywhere.

Denise van Huyssteen, a spokesperson for another of the companies in the suit, General Motors South Africa, said the company early on adopted the 1977 Sullivan Principles which encouraged more than 100 foreign companies to leave South Africa, a move that helped end apartheid.

The company's website says that in 1987 "growing internal pressure in the US on GM to leave South Africa finally forced the company to pull out".

Companies should be punished for their unethical behaviour, said Jody Kollapen, chairperson of the Human Rights Commission.

"I think it is clear that the principle of holding both state and non-state actors accountable for human rights violations has become part of international law," he said.

Lawrence Schlemmer of the Institute for Race Relations said he was "very cynical" about it.

"How far back do we go in history?" he asked. Would there be an Aborigine reparations trial in the United States, and one because northern Indians of Persian extraction mistreated southern Indians? And what about the way the British treated the Irish?

He did not think the case would hurt South Africa's economy but said there was a "bigger risk" for the rest of the continent.

"There are many governments which may yet blot their copy book ... and if one wants to get investment flowing into these countries people will say 'hang on. What if this chap does something alarming and there's a reparations trial and I as an American investor am held responsible?'"

That's as it should be, said Stephen Gelb, director of the Edge Institute for economic research.

He said: "I think if there are more cases like this then it will become a consideration, in effect a future contingency that they would have to take into account."