Recently released minutes of a 3 July 2003 meeting of the committee appointed to advise the government on GM, contain comments warning that organic oilseed rape grown in fields previously used for trials of GM oilseed rape is likely to breach contamination rules.
The Advisory Committee on Releases to the Environment (ACRE) notes that although farmers who have grown GM oilseed rape as part of government trials are banned from planting conventional rape seed in those fields for two years, contamination will be impossible to control even after this time and is likely to breach legal limits.
The committee notes: "Preliminary results from new research [has] shown that up to 5% of the crop which emerges could be GM contaminated, thus making it potentially unlawful to market the crop."
British law does not allow the sale of GM oilseed rape, and EU laws only allow up to 0.5% GM contamination from an unlicensed crop in food sold to the public.
The ACRE committee proposed that farmers who have taken part in GM trials should not grow conventional oilseed rape until more is known about the risk of contamination.
Pete Riley of Friends of the Earth, who opposed the GM crop trials, said: "This news highlights the threat GM crops pose to our food, farming and environment. The Government must not allow GM crops to be commercially grown in the UK.
"The Government must take steps to ensure that all farmers that have grown GM oil seed rape, and not just the ones that have taken part in the farm scale trials, are banned from planting rape in these heavily polluted fields."
Following the comments by the ACRE scientists, the government announced on Friday 25 July that farmers will not be allowed to plant conventional rape this autumn in fields that were used for trials of GM oilseed rape. The government said this was to "minimise any commercial consequence to [farmers] from GM plants accidentally growing from seeds left in the ground mixing with conventional plants."
The risk of contamination by GM crops has been a key issue in the debate over GM foods. In 2001, the EU's Scientific Committee on Plants proposed a five-year gap between GM oilseed crops and non-GM production, noting that the risk of contamination may arise for up to 10 years.
The government is expected to produce rules restricting how GM crops are grown so as to prevent contamination of conventional crops, after MEPs handed this responsibility to individual EU governments in a raft of GM legislation recently voted through the European Parliament.
The comments by the ACRE scientists come at the end of government's Farm Scale Evaluations programme involving the experimental growth of GM oilseed rape. Trials of GM crops in the FSE programme took place in secret locations following sabotage by environmental groups concerned at contamination and the implications of GM food.
In addition to oil seed rape, GM maize and beet crops were grown in trials. However, there trials have provoked less concern of contamination as maize seed cannot survive the UK winter and beet crops are prevented from setting seed.
The first set of results from the FSE programme is to be published by the Royal Society in autumn. The government has said that no decisions on the GM crop varieties used in the trials are expected before the end of the year.