A report published by the Food Commission, an independent consumer body, said that many supermarkets, which claimed to be aiming for GM-free products, were looking for a "tolerance level" which, while lying within legal limits, would still contain "unacceptable" levels of GM content.
The watchdog said that although "GM free should mean zero GM", realistically it was more likely that the permissible levels would be made as low as could be tested for, using current laboratory technology. That was equivalent to a maximum of 0.1 per cent. "We feel it is important to make this point now to alert people," said Sue Dibb, co-director of the commission.
"This aspect of GM food is one that most people probably aren't aware of.
"If the EC decides that `GM free' can mean `2 to 3 per cent GM', that's not going to be acceptable to consumers," she added.
Laboratory tests can detect GM ingredients more readily if a food is not highly processed. The more an ingredient is processed the more the identifiable DNA is broken up and tracing becomes difficult. Manufacturing processes can lead to "cross contamination" between GM and non-GM lines.
European food laws allow for tiny amounts of materials to appear in foods without being labelled. But sources within the European Parliament suggested that new laws, to be debated this autumn, could mean that food producers could include far more in their products.
In a report in Food Magazine published today, the commission asked main supermarkets what their limits were. Tesco, Marks & Spencer and Budgen said they required zero content. Asda, Iceland - the first chain to have said it had eliminated GM from own-brand products - the Co-op, Somerfield and Waitrose said they were allowing a higher tolerance limit, or waiting for an EU level to be set.
Ms Dibb added: "We are saying that the legal statutory requirement to label something as `GM free' should be that it contains no detectable GM ingredients above the 0.1 per cent level. The laboratory tests now have a limit of detection going down to 0.01 per cent but no lab would verify that; they refuse to verify figures below 0.1 per cent."Reuse content