They have acknowledged that meat, fish, eggs and dairy products on their shelves could contain “indirect” GM ingredients.
Every major supermarket in the country said it was unable to provide a guarantee that it was not selling products from animals given GM feed.
Even''high-end’’ retailers said only the more expensive organic ranges were certain to have been produced without any GM involvement.
The disclosures have reignited the debate about the use of genetic technology in food production following health and environmental concerns.
Opponents of the technology claimed that retailers were using a loophole in labelling rules to “trick” the public over the link to GM.'