The campaign is titled Greenwash Gold 2012, while the launch event will take place at the Amnesty International UK Human Rights Action Centre here this evening.

The launch will be chaired by Meredith Alexander, who resigned from her senior role on the Commission for a Sustainable London 2012 (CSL) in protest to Dow's involvement in the Games.

Alexander claimed she was stepping down from her unpaid position because of Dow's links to the 1984 Bhopal disaster.

Dow bought United States chemical firm Union Carbide, whose Bhopal plant in the Indian state of Madhya Pradesh leaked toxic gases in 1984, killing thousands of people in the world's worst industrial accident.

Following the Bhopal disaster, Union Carbide settled its liabilities with the Indian Government in 1989 by paying $470 million (£310 million/€351 million) for Bhopal victims and even though Dow bought Union Carbide a decade after the compensation deal, the company have been criticised for being a worldwide sponsor of the International Olympic Committee (IOC).

However, Dow is not the only target of the campaign, which also attacks London 2012 Tier One Partner BP, the Official Oil and Gas Partner of the Games, and Tier Three sponsor Rio Tinto, the Official Mining and Metals Provider of the Games.

Members of communities impacted by the three Olympic sponsors, from all over the world, have come together for the launch event to criticise the companies.

They include a survivor of the Bhopal disaster, a representative from the Gulf Coast where BP's catastrophic oil spill in 2010 took place and a community representative from Mongolia, where a Rio Tinto mine providing metal for medals is accused of exploiting scarce water resources in a desert region.

"Some of the most disreputable companies in the world are sponsoring the Olympics," said Richard Solly, a coordinator of the London Mining Network.

"Rio Tinto, Dow and BP all have appalling environmental and human rights records, and they are being allowed to greenwash their tarnished reputations by association with the 2012 Games.

"Greenwash Gold 2012 is providing people with an opportunity to name and shame the worst corporate sponsors of the London Olympics."

All three of the sponsors have been made the subject of a short animated film, by various award-winning animators, as part of the new online campaign and viewers will be encouraged to visit the Greenwash Gold 2012 website, where they will be able to vote for the worst corporate sponsor.

During the London 2012 Olympics, the organisers of the campaign will award "worst sponsor" medals to one of the three sponsors, based on the results of the public voting.

The Greenwash Gold 2012 website was launched today here.

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