Greenpeace protesters made a similar protest in Wales

More than a dozen demonstrators donned cow costumes to make their point at the Sainsbury's store in Sunderland.

The protesters claim the supermarket's own-brand milk is from cows fed imported GM animal feed.

The supermarket chain has insisted that its milk does not contain any genetically modified materials.

The action in Sunderland follows a similar protest in Wales a week ago.

Greenpeace campaigner Ben Ayliffe said: "The reason why GM is still coming into the UK is because supermarkets like Sainsbury's are selling milk from cows fed on GM.

Animal feed

"Shoppers in the North East have been clear on GM, they don't want to buy it and they don't want to see it on supermarket shelves.

"If Sainsbury's wants to live up to the claims it makes on its advertisements it should listen to its customers and stop selling GM milk."

Northumbria Police did not make any arrests.

A statement issued by Sainsbury's after the incident in Wales, said: "Customers can be assured that our milk does not contain GM materials and is sourced from the same farms that supply other supermarkets, like Tesco and Asda, as well as hotels, schools and hospitals.

"To offer our customers choice we have launched a milk from cows fed on animal feed guaranteed to be free from GM."

In June 13 Greenpeace protesters were remanded after illegally boarding a ship carrying GM crops in the Bristol Channel.