Supermarkets across Britain are routinely selling food from animals reared on genetically modified crops without having to declare it on labelling, it can be disclosed. They have acknowledged that meat, fish, eggs and dairy products on their shelves could contain “indirect” GM ingredients. Last night supermarkets including Iceland, Aldi and Lidl said they could provide no guarantee that meat, farmed fish, eggs or dairy products on sale did not come from animals given GM feed. Asda said “all livestock” could potentially have been fed GM products. Sainsbury’s and Tesco said poultry and animals for certain high value lines were fed a non-GM diet. But they could not guarantee animal products from most of the rest of the range. M&S and Waitrose, which promote a tougher stance against factory-farmed foods, sell processed food such as chicken sandwiches and ice cream produced from animals fed a GM diet. Pete Riley, of the campaign group GM Freeze, said: “No supermarket can claim to be non-GM, they might have aspired to be at one point, but effectively they have been pulling the wool over people’s eyes.” The disclosures have reignited the debate about the use of genetic technology in food production following health and environmental concerns.