ActionAid is to lobby jewellers over Christmas to make sure they comply with new laws on conflict diamonds.
From 1 January, all imported or exported rough diamonds must have a Kimberley Process certificate guaranteeing that they are conflict free.
More than 30 governments, the European Community and the diamond industry have signed up to the Kimberley Process Certification Scheme, which aims to ban the illegal trade in rough diamonds.
The certification scheme, which is the culmination of a six-year campaign started by Global Campaign, means anyone unable to verify the source of their diamonds could lose their licence.
Diamonds are at the root of some of Africa's most protracted conflicts in countries such as Liberia, Angola, Sierra Leone and the Democratic Republic of Congo where they are sold by warlords and unscrupulous traders free from regulation.
Alex Yearsley, Global Campaign's lead campaigner, said the focus of the charity's activity would switch to monitoring the effectiveness of the procedures.
"For the first time, a legal and credible diamond mining system has been established," he said.
ActionAid will target jewellers over the festive season to raise awareness of the new law. It has hired an agency to run a full-blown campaign in the New Year. Policy officer Amboka Wameyo said: "It is up to us to make jewellers and the public aware of the scheme."