NFU Scotland will today call on shops to put up prices immediately to prevent farmers and processors going out of business. Major farms are understood to be in talks with their bankers about emergency overdrafts.

Jim McLaren, the president of NFU Scotland said: "Pig farming is on a knife-edge and poultry farmers will go out of business within weeks unless the price paid at the farm gate increases. If producers give up, meat farming will never recover and we will be in the same position as we are with dairy farming, with shortages of local milk and rising prices."

He said an increase of up to one third was needed in the price for pigs but that this would mean paying no more than 13p extra for a packet of bacon.

Wheat prices have almost doubled in a year as flooding in world grain-growing areas coincides with rising demand from the biofuel industry, which uses grain to produce ethanol.

Mr McLaren said: "The effect of unsustainable cheap prices on dairy farming is evident: there is no longer enough production. The farms are gone. It has only just dawned on supermarkets that this will eventually lead to shortages and higher prices."