Global Witness said Monday it has left the Kimberley Process, accusing the international diamond regulatory group of refusing to address links between diamonds, violence and tyranny.
In a statement, the rights watchdog cited what it called failures in Ivory Coast, Venezuela and Zimbabwe.
"Consumers have a right to know what they're buying, and what was done to obtain it," said Charmian Gooch, a Global Witness founding director. "The diamond industry must finally take responsibility for its supply chains and prove that the stones it sells are clean."
Governments, the diamond industry and rights group have worked together as members of the Kimberley Process since 2003 to impose requirements on its members to enable them to certify rough diamonds as "conflict-free" so that purchasers can be confident they are not funding violence. The project was born after wars in Sierra Leone and Liberia that were fueled by "blood diamonds."
Last month, in a decision Global Witness called "disappointing" at the time, the Kimberley Process agreed to let Zimbabwe trade some $2 billion in diamonds from fields where human rights groups say miners have been tortured. Zimbabwe has denied allegations of human rights abuses in the fields.
Human Rights Watch has accused Zimbabwean troops of killing more than 200 people, raping women and forcing children to search for the gems in the fields.
"Over the last decade, elections in Zimbabwe have been associated with the brutal intimidation of voters. Orchestrating this kind of violence costs a lot of money," Global Witness's Gooch said Monday. "The Kimberley Process's refusal to confront this reality is an outrage."