Two conservation groups have told the International Whaling Commission (IWC) of a scam they say endangers Japanese consumers.

The groups are the UK-based Whale and Dolphin Conservation Society (WDCS) and the Swiss Coalition for the Protection of Whales (SCPW).

In their evidence to the IWC, holding its annual conference on the Caribbean island of Grenada, they claim about 1,800 tonnes of contaminated dolphin meat a year is creating a public health risk.

The groups funded research by scientists from Harvard university and two Japanese toxicology laboratories.

Sperm whales

The scientists analysed 130 samples sold as "whale meat" in six cities across Japan. DNA analysis showed that 25% of the samples were "mis-advertised" - they came from or contained a species different from the one offered for sale.

Japanese shoppers may not know quite what they are buying

Most of these samples were identified as species of dolphins and porpoises caught in Japanese coastal waters. Some samples contained meat from protected whale species, including two different humpbacks and two samples of sperm whale.

The scientists also found that 95% of the dolphin and porpoise meat contained at least one pollutant type above the levels set by Japan as safe for human consumption.

One sample contained mercury levels more than 200 times higher than Japan's maximum permitted limit. Others contained a range of organochlorines, which can accumulate in the food chain.

Developmental problems

Last year a 12-year study of the children of people in the Faroes who ate pilot whales showed a link between developmental problems and maternal exposure to chemicals.

Women were warned not to eat some pilot whale products until they had ended their child-bearing years. WDCS and SCPW say the study provides "clear evidence that unscrupulous processors and retailers are buying cheap meat from tens of thousands of dolphins and porpoises".

They say that in 1997 Japanese whalers killed 20,236 small cetaceans in the country's coastal waters.

These included Dall's porpoises, striped, spotted, bottlenose and Risso's dolphins, short-finned pilot whales, killer and false killer whales, and Baird's beaked whales.