LEAKED internal emails have revealed a massive cover-up by the British oil trader Trafigura, in one of the worst pollution disasters in recent history.

The emails obtained by The Guardian prove that Trafigura, which abruptly announced an offer to pay compensation to 31,000 West African victims, was fully aware that its waste dumped in Ivory Coast was so toxic it was banned in Europe.

Thousands of West Africans besieged local hospitals in 2006, and a number died, after the dumping of hundreds of tonnes of highly toxic oil waste around the country's capital, Abidjan. Local autopsy reports on 12 victims appeared to show fatal levels of the poisonous gas hydrogen sulphide, one of the waste's lethal byproducts.

Trafigura has publicly insisted for three years that its waste was routine, harmless and ''absolutely not dangerous''.