Traces of genetically modified soya beans which have not been licensed as safe for human consumption in Europe have been identified in products on sale in this country.
The Ministry for Agriculture Fisheries and Food is investigating a complaint by trading standards officers that the beans have passed into the food chain through the back door.
Government officials have also been involved in meetings with their European counterparts to try to devise a strategy for monitoring imports. "There are concerns that this might happen and it is being dealt with community wide," said a spokesman for the Department for Environment, Transport and the Regions.
The latest furore over genetically modified food follows a survey by Worcestershire trading standards officers. Tests by their scientists found that GM soya had been used in 60 out of 200 samples but only one of the products was properly labelled.
More worryingly, however, the tests also identified a type of genetically modified bean which is not licensed for sale in Europe. Only one soya - produced by the biotechnology giant Monsanto - has been granted a licence in Europe but the bean contained in the sample was not this strain. Scientists believe it was probably another type of GM soya which is legal in the United States but banned in Britain.
Clive Graham, one of the trading standards officers involved in the investigation, said he had been "very concerned" to discover the unlicensed soya. "This is an illegal ingredient and we are now investigating to try to trace the source," he said. "Maff has also been informed."
Carol Stevens, of Worcestershire Scientific Services, confirmed that the department's screening had discovered a "rogue element" in the samples. "The soya was genetically modified but it did not follow the same pattern as licensed GM soya," she said.
Pete Riley, a spokesman for Friends of the Earth, said the development was "extremely worrying." He said: "If this is true, the Government is rapidly losing control. Food which has not passed through UK safety tests is already in the food chain."
The only soya bean licensed for sale in Europe is Monsanto's Round Up Ready Soya, which was approved in 1996. The other soya has been developed in the US by AgrEvo, designed to be resistant to a particular weedkiller, but it is still unlicensed in the UK.