The final results of Government trials into the impact genetically modified crops have on wildlife were published yesterday, sparking condemnation among environmental campaigners.
The results show growing GM winter oilseed rape led to fewer plants beneficial for insects and birds and an increase in grass weeds.
Fewer bees and butterflies were found in the GM crop compared to the conventional crop.
The trials mark the end of a four-year £5.5 million farmscale evaluation launched by the Government following public concern over the impacts genetically modified crops have on the environment and public health.
They were carried out to assess the impact on farmland wildlife of growing GM crops compared with conventional crops.
Results for GM maize, beet and spring oil seed rape were published in October 2003.
GM oilseed rape and beet were judged to be more damaging to the environment than their counterparts.
Friends of the Earth said the results were a severe blow to the biotech industry and should not be used to justify the commercial go ahead for the controversial crops.
The lobby group claims 23 out of 25 EU countries, including the UK, objected to the GM crop being grown because of concerns about the impact on the environment and human health.
Clare Oxborrow, Friends of the Earth's GM campaigner, said: "These results are yet another major blow to the biotech industry.
" Growing GM winter oilseed rape would have a negative impact on farmland wildlife. Almost every EU country has raised serious concerns about the impact that this crop could have on our environment and health.
"The farm-scale evaluations only looked at a narrow range of concerns. They were not a comprehensive assessment of the risks of growing GM crops.
"The vast majority of consumers have made it clear that they do not want GM. The Government should pull the plug on this unnecessary and unpopular technology."
The results will now be passed to the Government's statutory advisory body - the Advisory Committee on Releases to the Environment.