A total of five protests took place at depots up and down the country

The protesters said they were trying to stop the firm from distributing dairy products that come from cows fed on genetically modified animal feed.

Sainsbury's said there was "no evidence" that milk from animals fed on GM crops contains any GM material.

Depots in Bristol, the West Midlands, Essex, South Yorkshire and Merseyside were all targeted on Friday.

The protesters said the action was taken "in solidarity" with farmers.

Lorries delayed

"Neither farmers or consumers want GM in our food chain," said a protester.

"Sainsbury's must keep their promise to phase out its use, and pay farmers properly so they can do so."

At Waltham Abbey in Essex, six protesters managed to stop lorries leaving and entering a distribution centre.

In Rotherham, South Yorkshire, between eight and 10 people blockaded the entrance to a depot and in St Helens, Merseyside, police said there were between 20 and 25 protesters.

The Food Standards Agency has categorically stated that there is no evidence that milk from animals fed on GM crops contains any GM material Sainsbury's statement

About 20 campaigners chained themselves together during a five-hour protest in Emersons Green, Bristol, delaying several lorries. No arrests were made.

Warwickshire Police said 22 people blocked a road near to a depot on the Hams Hall Industrial Estate, Coleshill, at 0200 BST on Friday, leading to 12 arrests.

It is understood police were waiting at the distribution centre after the supermarket chain learnt of a possible demonstration.

Some protesters secured themselves to obstacles which they had erected across the road while others linked themselves together, police said.

The group voluntarily released themselves at about 0730 BST and were then arrested for obstructing the highway.

'Highly regulated'

A total of 50 officers were involved in the Warwickshire dispute, which police described as peaceful.

A statement from Sainsbury's read: "Our milk does not contain GM ingredients.

"Milk is highly regulated and, like all supermarkets, we are subject to stringent food safety controls.

"Our milk is sourced from British dairy farms that supply other UK supermarkets, like Tesco and Asda, as well as hotels, schools and hospitals.

"The Food Standards Agency has categorically stated that there is no evidence that milk from animals fed on GM crops contains any GM material.

"To offer choice to our customers we have launched a new milk from cows fed on non-GM feed which is now in over 100 stores."