UK supermarket chain Asda has come bottom of a league table produced by environmental lobby group Greenpeace ranking supermarkets on their seafood policies.

The supermarkets were marked out of twenty across four categories: number of the most destructively fished species sold, seafood procurement policies, support and promotion of sustainability initiative, labelling policies and public promotion of sustainable seafood.

Asda notched up just one point out of 20, Tesco got five and Sainsbury's ten. US-owned Asda was found to be selling at least thirteen species on the Greenpeace 'danger list' including swordfish, dogfish (shark) and Atlantic cod.

Marks & Spencer, on the other hand, topped the league with seventeen points and was found to have a comprehensive, transparent policy. This is largely reflected by what food M&S sells, in addition to supporting research and promoting sustainability initiatives, Greenpeace said. Waitrose also impressed, with fifteen points.

The total UK retail market for seafood is worth £1.8bn (US$3.2bn) a year, with nearly 90% of sales made through supermarkets.

"Asda did worse than we'd thought possible, and they fully deserve their bottom-drawer ranking. They stock at least thirteen species of threatened fish and have no public policy on the sustainability of the fish they sell. Asda and other supermarkets should take immediate action to remove the most destructively fished species from their shelves. Then they should follow the lead of Marks & Spencer and Waitrose and start sourcing seafood that comes from healthier stocks, caught using less harmful fishing practices," said Greenpeace campaigner Oliver Knowles.