Annie Dunnebacke, from London-based Global Witness, said the Kimberley Process Certification Scheme has been unable to "effectively address issues of noncompliance, smuggling, money laundering and human rights abuses in Zimbabwe's diamond fields."

The Kimberley Process, established in 2002, aims to stem the flow of "blood diamonds" being used to fund fighting across Africa. Participants are forced to certify the origins of the diamonds being traded. This assures consumers that by purchasing diamonds they are not financing war and human rights abuses.

Zimbabwe has been crippled by an economic and political crisis, which many blame on President Robert Mugabe's 28-year-rule. There has been little change since Mugabe entered a unity government with former rival Morgan Tsvangirai earlier this year. Many fear that Mugabe will not relinquish his hold on the country.

The Kimberley Process risked losing its credibility if diamonds from Zimbabwe were not classified as "blood diamonds" and called for it to be suspended from the international body, Dunnebacke told The Associated Press on the sidelines of a three-day meeting of the Kimberley Process.

A review team from the Kimberley Process is due to visit Zimbabwe next month following an earlier visit in March this year in which it only met with government officials.

Bernhard Esau, the Namibian deputy minister of mines and current chairman of the Kimberley Process, said there were "gaps that can be strengthened" in order to stem the flow of diamonds being illegally exported from Zimbabwe.

"It is our aim to curb the flow of illicit trade, therefore we need to continue strengthening the security system and improve our internal control," Esau told delegates at the opening of the meeting.