GENETICALLY-modified food is entering the UK by stealth via feed given to animals reared for dairy and pork products, a campaign group has warned.
Supermarket chains are widely stocking goods sourced from animals fed GM soya and maize, according to the Soil Association.
GM material could find its way, in small quantities, into the milk and animal tissue of GM-fed livestock, the group said.
The Soil Association, which is pro-organic, said consumers were eating food produced from GM crops without their knowledge.
There is no requirement to label food produced from GM-fed animals.
Most supermarkets have not banned dairy and meat products from GM-fed animals, despite banning GM ingredients from their own-label products, according to the association.
Tests carried out on 35 feed samples from dairy, pig and poultry farmers found 73 per cent contained GM soya.
Of the GM soya samples, 27 per cent had a GM soya content of more than 70 per cent.
Supermarket and feed company sourcing policies showed that GM maize was also widely used, with the dairy and pig sectors most likely to do so.
The Soil Association is calling on the government and the European Commission to bring in compulsory labelling for foods produced from GM-fed animals.
Patrick Holden, director of the association, said the findings were alarming.
"This amounts to deception on a large scale," he said. "This is not just accidental contamination, hundreds of thousands of tonnes of GM grain are being used to produce our food each year.
"Biotechnology companies have clearly used imported animal feed as a 'Trojan horse' to introduce GM into the UK food chain, despite the fact that the British public have voted overwhelmingly against GM."
It says the Little Red Tractor and Freedom Foods labels do not guarantee that products have not come from animals fed on GM food.
