A trustee of Nelson Mandela's charity has resigned after revealing that he accepted diamonds from British supermodel Naomi Campbell in 1997.

Jeremy Ratcliffe, who was head of the Nelson Mandela Children's Fund at the time, admitted to keeping the stones after Campbell mentioned them in testimony at former Liberian president Charles Taylor's war crimes trial at the Hague.

Prosecutors had been trying to prove the gems were "blood diamonds" given to Campbell by the former Liberian leader after a charity dinner in South Africa.

Campbell had said she received "a few dirty stones" from two men who told her it was a gift. Campbell testified she assumed the stones were from Taylor, who is accused of supplying weapons to Sierra Leone rebels in return for diamonds.

The board of Nelson Mandela's charity said Ratcliffe apologized for his secrecy about the diamonds on Wednesday, and said he kept the stones out of concern the charity might be implicated in something illegal.

Ratcliffe said he gave the diamonds to South African police after Campbell named him in her testimony.

Some information for this report was provided by AFP and Reuters.