Defra has announced new proposed guidelines to govern the potential production of genetically modified crops in the UK.
If the suggestions are agreed upon, GM crops grown in the UK would have to be separated from non-GM fields by at least 35m (114ft).
The measure is designed to minimise “crop mixing”, should the European Union approve cultivation of GM crops.
Defra's suggestions set minimum separation distances for any GM crops grown in England, ranging from 35m (114ft) for oilseed rape to 110m (361ft) for maize grown for human consumption.
There are no suggestions for fresh produce as, to date, no commercial GM crops have been grown in the UK.
Immediately, the pressure groups countered the Defra proposals, however. Sue Mayer of Genewatch UK said the proposals were designed to limit "contamination" of non-GM crops to 0.9 per cent.
European regulations mean that foods containing more than 0.9 per cent of genetically modified ingredients have to be labelled as GM produce, even if farmers had set out to grow conventional varieties.
"Under the Department for Environment, Food and Rural Affairs (Defra) proposals, GM contamination of non-GM crops would be the norm, and a genuine GM-free choice won't be possible," said Mayer.
"Another key question is the extent to which it is going to be possible to enforce and police any co-existence measures, particularly for crops such as oilseed rape which are grown on a large scale."
Other proposals that appear in the UK government consultation paper include a public biotech crop register.
