The effectiveness of a plan to filter out so-called blood diamonds is under review at a conference in Botswana. A recent report about diamonds being smuggled out of Ivory Coast will top the agenda.

Representatives from the 47 member countries of the Kimberley Process are meeting in Botswana's capital, Gaberone, for a three-day conference to discuss how well conflict diamonds are being kept out of the market.

The three-year-old Kimberley Process is a certification plan, set up to ensure that diamond proceeds do not fuel war.

Diamond giant De Beers has joined human-rights groups in calling for a crackdown on blood diamonds, after reports that many illegally enter the legitimate market.

In the firing line is Ivory Coast. A recent U.N. Security Council report says rebels who control the north are contravening a year-old embargo, which was imposed, because of fears that diamond money may be going towards purchasing weapons.

Vehicle passes through Ivory Coast diamond checkpoint

Despite the ban, between $9 million and 23.5 million worth of rough diamonds are leaving Ivory Coast every year, the report says.

The U.N. Group of Experts researched the report. Its Chairman, Alex Vines, said the northern rebel New Forces are in control of the biggest mining site, the Bobi Dyke near the town of Seguela.

He said, "They have a military base right next door to it. So the Group of Experts was in no doubt that the military were organizing the activities at the Bobi Dyke. The New Forces certainly benefited from it."

The New Forces deny directly benefiting from any diamond trade.

The group of experts have now presented their findings to the Kimberley Process meeting.

Also implicated are Ghana, which is a member of the scheme, and Mali. They are apparently receiving the smuggled diamonds and trading them as clean products.

The U.N. experts say Ghana's diamond-production levels have continued to rise considerably, even though few new reserves have been found.

Vines says Kimberley members may decide to punish Ghana for loose controls.

"One of the measures they could consider is suspension of Ghana from the Kimberley Process until their internal controls are better," he said.

The Republic of Congo was suspended for similar reasons in 2004. Ghana denies the allegations.

The diamond industry is especially worried as its peak pre-Christmas sales may be threatened by next month's Hollywood release called "Blood Diamond."

The industry fears the film could reduce consumers faith in the diamonds they want to buy, as they may be concerned about where the money they pay for it goes.