Thousands of South Africans who suffered under apartheid won the right yesterday to sue a number of companies, including BP, Citigroup and Ford, for allegedly helping to perpetrate human rights abuses.

The US Supreme Court ruled that three class actions can use the American legal system to sue approximately 50 international corporations who they believe “knowingly aided and abetted the South African military and security forces”. Some legal experts have estimated that the companies could be sued for as much as $400 billion.

The corporations that could be facing a court challenge in the United States also include ExxonMobil, UBS, Deutsche Bank, General Motors, IBM, Hewlett-Packard, Bank of America and General Electric.

The three class actions are believed to represent thousands of South Africans who suffered under apartheid between 1948 and 1994. One set of plaintiffs - a South African human rights organisation called the Khulumani Support Group - said that it had 32,700 members who were survivors of apartheid violence.

Lawyers representing the victims within the three class actions will have to establish that the companies knowingly helped the South African government to perpetrate human rights abuses. That could include, for example, proving that a motor company knew that lorries that it sold in South Africa would be used as armoured vehicles to destroy townships. It could also include establishing that a technology company sold computer equipment and software that would be used to operate a racial identification system.

Speaking to The Times, Michael Hausfeld, the lead counsel for the Khulumani group, which is based in Washington, said: “We want a legal acknowledgement of accountability, that these international corporations knowingly helped the regime violate human rights.

“A ruling in our favour would have two possible impacts. It would force the companies to pay compensation to those who were injured as a consequence of the abuses they suffered. It would also trigger a change in corporate governance.”

In a hearing in July, Mr Hausfeld said that he would ask the court to demand that the companies produce documentation about their business in South Africa up to 1994, which would show “what they did and what they knew”. It is possible that representatives of the companies would have to appear in a court in New York.

The lawsuits were filed in 2002 and were thrown out by a federal judge on the ground that the United States's courts did not have jurisdiction.

This case is the latest test of an 18th-century law, called the Alien Tort Claims Act. It allows foreigners to use the US legal system to right international law violations. The legislation was drawn up to help foreigners seek redress for issues such as piracy, but it has been used increasingly to sue corporations for their alleged involvement in human rights abuses overseas.

Last year, Yahoo! was sued for its decision to give China access to a political dissident's e-mail account. The online search engine settled.

The American and foreign corporations have appealed to the Supreme Court. The Bush Administration and business groups have supported their appeal.

BP failed to return calls. UBS declined to comment and Deutsche Bank and General Motors were not available to make any statement.

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