Scientists meet tomorrow for a conference marking the 25th anniversary of a research programme into whale deaths around our coasts.

Experts will discuss post mortems into 3,500 stranded whales carried out by the Cetaceans Strandings Investigation Programme, since it was launched in 1990.

Recent deaths include 29 sperm whales which stranded around the southern North Sea in January and February, on beaches including Hunstanton, Old Hunstanton and Skegness.

Scientists have found high levels of pollutants in the carcasses of many whales they have examined.

Tomorrow's conference is expected to hear that flame retardants and other man-made chemicals have been linked to the deaths of Atlantic killer whales and dolphins.

But Rob Deaville, project manager with the CSIP, said: 'It does not relate to and is unlikely to be a significant factor in the sperm whale unusual mortally event earlier this year though.

'Sperm whales feed at a lower trophic level and are unlikely to accumulate as significant a level of contaminants as other odontocetes in the North Atlantic.'

Biologists are still unclear why the whales stranded in Norfolk, Lincolnshire and off the Dutch and German coasts earlier this year.

One theory is that the creatures came south down the North Sea in search of food, before becoming disoriented in shallow water.

Staff from Hunstanton Sea Life Sanctuary, coastguards and lifeboat crew tried to save the animals by driving them back out to sea.

But beached whales almost invariably die, as their internal organs are crushed by their own weight without water to support them.

Thousands travelled to see the animals, before they were cut up and taken away to be disposed of in landfill.