Concern that seeds from GM oil seed rape crops stay in the soil longer than previously thought has led to a new warning being issued to farmers.
GM crops were trialled in Scotland for three years
The Scottish Executive has advised farmers who planted GM oil seed rape as part of government trials not to sow conventional varieties of the crop in the same fields this year.
Preliminary findings from a government-commissioned report have led the executive to issue the advice to ensure GM oil seed rape does not accidentally enter the supply chain.
The precautionary measure has been agreed between the executive, Defra (Department for Environment, Food & Rural Affairs) and the Advisory Committee on Releases to the Environment (Acre).
Farmers in Scotland grew GM oil seed rape as part of a three-year Farm-Scale Evaluation (FSE) of genetically modified crops.
The FSEs studied what effect the use of weed killers with the GM Herbicide Tolerant crops might have on farmland wildlife.
Deputy Environment Minister Allan Wilson said:
"Throughout the conduct of these farm scale trials we have been entirely clear that our first priority is to protect public health and the environment. There continues to be no risk to either.
"This action is aimed at preventing GM material from trial crops turning up in any subsequent conventional crop and will enable farmers to eradicate any remaining GM plants with herbicide."
The farm scale evaluations programme has now been completed and the first set of results is to be published by the Royal Society in September.
The preliminary findings of the report suggests that oil seed rape seeds (both GM and conventional) persist in greater quantities in the ground than had previously been found.
The research will be made public as soon as it has been finalised.
There are no similar concerns with the other GM crops being trialled in the UK - maize seed cannot survive over winter in the UK and beet crops are prevented from setting seed.