The group, which gathered at the Somerfield depot in Bridgwater, Somerset, on Thursday night, complain that consumers believe foreign meat which has been processed in the UK is British because of inadequate labelling.

"Britain has higher standards of hygiene and welfare than anywhere else in Europe," said a spokesman for the British Pig Industry Support, which organised the protest.

Fresh pork is mainly British but bacon can come from a number of different countries

The spokesman said pork presented the biggest problem because, although most of the fresh produce was British, bacon, sausages and processed meat could come from a number of different countries.

"All the information we have is that shoppers want to buy British pork, because they know it has come from a high welfare system, but they are not being given enough information to do so," he said.

Organisers claimed 300 farmers and their families took part in the demonstration, which tried to stop lorries entering or leaving the depot, but Avon and Somerset Police said the figure was closer to 100.

Pig farmers say they are losing out against cheap imports because they ensure high standards of welfare for their animals and will only use certain types of feed. This pushes up the price of their produce.

'Lure of cheap meat'

A farmer who took part in the protest but wished not to be named said supermarkets put pressure on the British to improve the welfare of their animals but then abandoned them in favour of cheaper imports.

He said: "Farmers in most states in Europe used to export to the Far East, but with the collapse of the economy there about a year ago they lost their market.

"Now they are dumping their meat in Britain, and the supermarkets cannot resist the lure of cheap meat."

A survey commissioned by the British Pig Association last November found that improved labelling on British pork products was encouraging sales.

'Early retirement'

Meanwhile, farmers hit by the BSE crisis and plummeting livestock prices could be offered up to £40,000 to retire from the industry, according to newspaper reports.

The plan being considered by Agriculture Minister Nick Brown would target the most vulnerable sectors of British agriculture, such as beef and sheep farming.

A growing number of farmers are dumping or killing young animals because they say they cannot afford to keep them or have them slaughtered.

The Times reports that the plans include offering farmers almost £20,000 in two successive years as an inducement to leave the land.