This was supposed to be the year that the jewellery at the Oscars, at least, would be conflict-free. Hollywood loves a cause, and the movie Blood Diamond - which has garnered Leonardo DiCaprio a nomination for best actor - gave the industry a perfect excuse to develop an instant conscience about the origins of the bling adorning its actresses.

As with the awards themselves, though, conflict runs inevitably just beneath the surface. So while human rights groups such as Amnesty International and Global Witness are distributing diamond-free teardrop-shaped pins to attendees of tonight's Academy Awards ceremony - all the better to raise awareness about the insidious role of diamond smuggling in African civil conflicts - the diamond companies themselves are fighting back with their own celebrity-targeted campaign.

Companies led by De Beers, the world's pre-eminent diamond trader, have spent millions to persuade stars, including Patricia Arquette and Sarah Jessica Parker, to wear diamond rings in return for a donation to South African charities. They have approached several other high-profile celebrities in the hope of scoring the kind of coup at the Oscars that they did at the Golden Globes last month, where both Beyonc� and Jennifer Lopez turned up on the red carpet flashing diamond jewellery.

Blood Diamond has caused the diamond industry a huge headache, because it makes a �40bn industry look like a kind of bloodsucker feeding on the misery of others. The problem was indeed huge during the 1990s, which is when Blood Diamond is set. Thanks to an international treaty known as the Kimberley process, signed in 2003, conflict diamonds are now estimated by the United Nations to account for just 1 per cent of the industry total - a fact that gives De Beers some cause to feel wrongly demonised.

Pressure groups counter that the Raise Your Right Hand initiative, being mounted by the Diamond Trading Company, a De Beers subsidiary, is no more than a cynical marketing campaign that does nothing to help those whose lives have been devastated in war zones such Sierra Leone.

Amnesty and Global Witness say they hope their "red teardrop" campaign will make consumers think about the jewels they buy and where they have come from. They have also highlighted what they see as flaws in the Kimberley process and note that even 1 per cent of the diamond trade - �400m - is too much.