Diamond buyers have been urged to boycott a top Bond Street jewellers amid fears the construction of a new mine in Botswana could jeopardise the return of one of the world's oldest tribal people to their ancestral homeland.

Leading tribal rights advocacy group, Survival International, is holding a protest on Tuesday outside Graff Diamonds, in New Bond Street, to draw attention to the plight of the San bushmen, who are believed to be the oldest people in Sub-Saharan Africa.

Numbering around 3,000, the bushmen were evicted from their land in the Kalahari central reserve in 2002 and forced by the Botswanan government to live in squalid 'resettlement' camps, where HIV and other diseases are rife.

In late 2006, a court in Botswana ruled the eviction was illegal, paving the way for their return - although many have yet to do so.

During the hearing, the Botswanan government denied it had driven the bushmen out to make way for diamond mining, instead claiming the San needed the schools and clinics provided in the resettlement camps.

But Survival International says plans for a diamond mine in the reserve - to be dug next year by mining firm Gem Diamond - will create a new obstacle for the San's return to their homeland.

Graff built up a major stake in Gem Diamonds before Christmas, acquiring around 10 per cent of the company.

There is no suggestion that Graff, or Gem Diamonds, has forced the San off their land, but Survival International believe Graff's share holding means it has a "moral imperative" to consider the fate of the bushmen.

"Most leading mining and jewellery companies have an 'indigenous policy' based on consultation and consent with the people who own the land, and if Graff doesn't have one, it ought to," said a spokeswoman for Survival.

"Consumers have a choice to buy diamonds, but I think they should excerise that choice with the knowledge of what is happening to the bushmen.

"The issue of blood diamonds caused a shift in public perception of the diamond trade. We hope the bushmen's story - although it is not the result of war - will again raise the question of where and how diamonds are sourced."

Graff Diamonds refused to comment on the issue.

In December last year the company, which is owned by Johannesberg-based jeweller Laurence Graff, bought a 478-carat diamond from Lesotho - South Africa - for $18.4million. The average price per carat was $38,400.

The diamond trade contributes around $8.4billion annually to Africa and, since the introduction of the Kimberley Process, which requires rough diamonds to be transported across international borders in tamper-proof containers with serial numbers, 99.8 per cent of diamonds traded are certified.

Botswana produces diamonds worth $3.2bn annually.

Picture courtesy of Survival International