The NFU has warned the government that restrictions on the feeding of GM foodstuffs to livestock might result in a shortages of meat products.

The farmers' body says that the "current intentions of several supermarkets will disrupt the supply of British meat, not just to those stores but to all retailers and caterers".

The warning comes as Marks and Spencer becomes the latest retailer to say that none of the meat it sells comes from animals fed on GM rations.