Gillian Anderson and Sophie Okonedo are among the film stars boycotting diamonds from Botswana as part of protest about the treatment of a local tribe.
Joanna Lumley, actor Mark Rylance and children's author Quentin Blake are also backing the protest by human rights group Survival International, prompted by reports the mythical Kalahari Bushmen natives have been kicked off their land so ruthless diamond diggers can mine.
The bushmen were relocated from their land in 2002 after diamonds were discovered there and, despite a court ruling in 2006 allowing them back to the area, they are still barred from accessing a borehole which was their only source of water.
And the stars are calling for a boycott of the De Beers diamond store in London, as well as one in San Francisco, until the situation in southern Africa is resolved.
Stephen Corry, Survival International's director, says, "People should know that far from being an expensive token of eternal love, Botswana diamonds are a symbol of the nasty oppression of southern Africa's first people."