The latest Kantar figures show fresh and frozen pork sales were up 6.2 per cent in the four weeks ending on 22 February.

Over the same period bacon was up 1.7 per cent, pork sausages rose by 6.4 per cent and sliced meat showed a 5.4 per cent increase.

Mr Lamb said: "That means, over the period there was an extra 2,500 tonnes sold and that is during a period when the meat and poultry market overall was falling slightly.

"Those increase in sales of pig meat are being driven mainly by deep cut promotions featuring cheap imported pork, two-thirds of which will have been produced under conditions which would be illegal in this country.

"This must be set against a falling pig breeding herd across Europe – a trend which is expected to continue over the next few years.

"Overall, the European Union breeding herd fell by nearly 3 per cent last year, based on census returns from 17 member countries."

BPEX Chairman Stewart Houston said: "Some retailers are being very supportive but others need to be aware of this and to take it into account in both their short and long-term sourcing policies or they could face serious supply problems."