PIG farmers in Yorkshire were blockading an Asda distribution centre early today in protest at the supermarket chain's "Roll Back" policy.

The farmers, who have been losing money for two years, targeted a depot in Normanton, Wakefield, and blocked the gates to its fresh produce exit.

Around 80 farmers arrived there yesterday evening and stayed outside the gates until the early hours of this morning.

Farmer John Rowbottom, from Melbourne, near York, said the event had been a success in as far as an Asda manager had agreed to contact him today to arrange a meeting.

He said: "We wanted an explanation for their Roll Back policy on British pig meat when we're losing money.

"They're refusing to pay the producers more for British produce.

"What they're saying is 'Sell us your pigs at a loss, or we'll import even more cheap pig meat from the Continent'.

"It's a sad day when we have to come to this kind of action to make our point."

He said he had previously asked for a meeting with Angela Spindler, head of meat and produce, based at Asda's Leeds headquarters, but had been refused.

He said the farmers argued that supermarkets should buy British because the practice of feeding animal meat and bonemeal to pigs was banned, sows were not kept in narrow cages in which they could not turn round, and male pigs were not routinely castrated without anaesthetic.

He also claimed Asda had threatened to remove the British mark of distinction from British pork because of an advert by the Meat and Livestock Commission which showed the conditions some pigs were kept in abroad.

Rachel Fellows, spokeswoman for Asda, said the only pig meat imported by the supermarket was a small amount of back bacon from Holland, and since last August, Asda had insisted that the Dutch suppliers complied with the same welfare regulations as British pig farmers.

She said this was because there was not enough back bacon of the quality required by Asda produced in Britain to meet demand.

"Roll Back was widely welcomed by farmers and since it was brought in we have sold 15 per cent more loins and chops, and 26 per cent more leg meat. That means we are selling more British products."

She said Asda had not asked for any money towards the cost of discounting goods for Roll Back and was still paying the same price to British farmers.

She admitted the store had been very concerned about the Meat and Livestock Commission advert because none of the pig meat sold by Asda had been produced in the conditions it showed.