Dolphins, whales and sea lions are among the species being killed by tributyltin (TBT), one of the most toxic chemicals deliberately released into the marine environment.

Sea otters are also dying off the Pacific coast of America as are birds and fish in the Atlantic.

The chemical is used in anti-fouling paint and applied to ships hulls to stop marine creatures sticking to the bottom of them.

Chemicals from the paint spread into the surrounding sea water and accumulate in sediments around harbours and along shipping lanes.

This is then ingested by marine invertebrates and gets into the food chain.

Ban call

Details of the latest research findings from America will be presented to a meeting of The International Maritime Organisation.

Head of the WWF-UK Marine Programme, Dr Sian Pullen, said: "The use of organotins in antifouling paints should be banned as soon as possible.

"The toxic effects of these chemicals on marine wildlife has been reported for over 20 years and now we are seeing sea otters dying, dolphins and seals' livers are being poisoned by this highly toxic substance.

"The only way forward lies in a world-wide ban on the use of organotins in antifouling paints by 2001 and the development of environmentally friendly alternatives."

A joint programme in Germany between WWF, ship owners, paint manufacturers, government and academic bodies has been looking at alternative biocide free paints.

The first results are said to show clear evidence that organotin and biocide free paints do work.

By 2001 a range of alternatives to TBT based paints, will be well established making this ban a realistic proposition for the IMO.

The WWF said the chemical continues to pose a threat to marine wildlife, not only to their food base, but directly to health and reproductive success by interfering with sex organ development.

TBT also attacks the thymus gland, suppressing the immune system, reducing the animal's ability to fight infection and making them more susceptible to disease.