The most ethical Olympics ever? Not according to Boris's 'ethics tsar'

One of Boris Johnson's "ethics tsars" will quit her post today over the controversial Olympics stadium contract awarded to an American chemical company.

Meredith Alexander stands down after accusing Olympics organisers and the 2012 ethical watchdog of acting like "apologists" for Dow Chemical by publicly repeating the company's own public relations line on human rights.

Lord Coe, the 2012 chairman, and the Games organisers Locog, have faced criticism from MPs, Olympians and human rights groups including Amnesty International and Bhopal Medical Appeal, ever since Dow was awarded a sponsored fabric "wrap" around the outside of the Olympic Stadium in a deal worth £7m.

Dow is the 100 per cent owner of Union Carbide Corporation (UCC), which was the majority shareholder of Union Carbide India Limited [UCIL], the company responsible for the 1984 gas disaster in Bhopal, India, which killed 25,000 people.

Campaigners say the continuing water contamination is responsible for high rates of congenital deformities and cancers among communities living around the old factory site.

Ms Alexander was appointed to the Commission for a Sustainable London 2012 by the Mayor in 2009 for her expertise in trade and workers' rights. It is the official watchdog set up to ensure London 2012 meets its commitment of being the most sustainable Games ever.

Dow bought Union Carbide in 2001 and denies any responsibility for UCC liabilities in Bhopal – which Locog accepts. Dow claims the $470m paid in 1991 for the disaster victims (currently contested in the Indian Supreme Court) was final. Yet Dow and UCC are defendants in an Indian litigation case about cleaning up the site.

Ms Alexander, who is head of policy at the charity Action Aid, told The Independent that Locog's failure to properly examine Dow's ongoing responsibilities to Bhopal was "inexcusable".

The "deal breaker" for her was a letter from the Sustainability Commission's chair, Shaun McCarthy, stating that it was satisfied with Locog's decision to work with Dow. "That letter has been used to justify Dow's position that it has no responsibility for the ongoing human rights tragedy in Bhopal," she said. "I cannot have my name associated with that.

"To my mind it is inexcusable that Locog did not find reference to Bhopal when they looked at Dow from a sustainability perspective. A two-second search on Google would have done it. This is not consigned to history – the site is still an ongoing environmental disaster. It's totally unjustifiable."

Ms Alexander's resignation comes as a blow because the Commission's work to ensure compliance with workers' rights – her area of expertise – is still outstanding. She is largely complimentary about the Commission's work. The Commission and Locog have never met Bhopal victims or survivor groups. Ms Alexander said: "Firstly, Locog didn't even know that this was going on, and then when they did find out, they only listened to one side of the story."

Lord Coe has defended Dow's record on Bhopal, telling MPs: "We have looked at this, and we are satisfied that Dow were not the owners or the operators or were involved with that plant at the time of the disaster, and at the time the overall settlement was made."

Dow's corporate social responsibility policies are in part why it was awarded the contract over five other bidders, according to Olympic organisers.

* 2012 wrap stays despite Olympics resignation