Belgian scientists have discovered a fragment of unidentified DNA in Monsanto's genetically modified Roundup Ready soya, and environmental group Greenpeace is now putting pressure on the UK government to ban the sale of the crop.

The discovery, which was reported in the European Journal of Food Research Technology, points to the existence of "a DNA segment of 534 bp DNA for which no sequence homology could be detected" and Greenpeace argues that this should be enough to prompt regulatory bodies to withdraw the soya from sale immediately.

Monsanto is adamant however that the discovery is not new to its scientists and that it poses no safety risk. From the company, Tony Combes told BBC News Online: "[the unidentified DNA] would have been a constituent of the Roundup Ready soyabeans used in all the safety assessment studies [...] There is no discrepancy. The sequence information provided originally has not changed; it's just that now we know more detail about it."

The UK government is counselled on GM crop safety by the Advisory Committee on Releases to the Environment, which said it was satisfied with Monsanto's revised risk assessment in light of the Belgian find.