A study of genetically modified crops in the UK found today there was no evidence that they are harmful to the environment.
The Bright project focused on GM sugar beet and winter oilseed rape which is tolerant to some herbicides compared with non-GM cereals grown in rotation over a four-year period.
It found the GM crops, used in rotation, did not deplete the soil of weed seeds needed by many birds and other wildlife.
The Botanical and Rotational Implications of Genetically Modified Herbicide Tolerance (Bright) Link project was sponsored by the Department for Environment, Food and Rural Affairs (Defra) and the Scottish Executive Environment and Rural Affairs Department (Seerad).
It was carried out by a group of research partners and industrial partners and co-ordinated by Dr Jeremy Sweet, of the National Institute of Agricultural Botany.
The aim of Bright was to mimic normal agricultural practice and measure how GM crops performed in a crop rotation.
As well as finding no evidence of seed depletion, there were also some potential benefits to farmers of growing the GM crops, according to the study.
The findings come as the GM debate gathers pace in the UK.
Earlier this year, Government advisers said farmers who grow genetically modified herbicide-tolerant maize crops under strict rules would not see adverse effects on wildlife.
But the Advisory Committee on Releases to the Environment (Acre), which studied the results of a three-year field scale trial of crops, said GM beet and spring-sown oilseed rape would have a negative impact on arable weed populations with a knock-on effect on birds and insects.
In September, a survey showed public attitudes to GM foods were hardening.
More than six out of 10 people (61%) polled on behalf of the consumer magazine Which? said they were concerned about the use of GM material in food production - up from 56% in 2002.
A Defra spokesman welcomed the publication of the results, which he said would be "considered carefully".
He said: "The report will be forwarded to the Advisory Committee on Releases to the Environment for consideration and we expect Acre will publish its advice on the report next spring."
But he added: "While this report is important and will be considered carefully, the earliest possible date for the cultivation of GM herbicide-tolerant crops in the UK is 2008."
The views of other interested organisations on the report would also be looked at, he said.
Friends of the Earth said the results appeared to confirm fears that, if released commercially, GM crops would be difficult to control and would cross-pollinate with non-GM crops, which would pose a "real threat" of contamination for conventional varieties.
The environmental group's GM campaigner Emily Diamand said: "This new research highlights yet again the risks of allowing GM crops to be grown commercially in the UK.
"Conventional oilseed rape would be threatened with GM contamination, and GM 'superweeds' could add to problems for farmers. It is little wonder that GM food and crops are so unpopular.
"It is high time the biotech industry abandoned its plans to grow GM food in the UK. The Government should stop supporting GM crops and concentrate on sustainable methods of farming instead."
FoE said the new research should offer little comfort to the biotech industry, adding that any suggestion it could be used to push the case for GM commercialisation would be "clutching at GM straws".
Dr Jeremy Sweet, scientific co-ordinator of the Bright project, said: "Regulations in Europe require that assessments are made of the impact of GM crops on the environment through changes in farming systems. Bright is the first UK study into how different herbicide-tolerant crops will interact with other crops in rotations.
"Our research indicates that there was no long-term difference in weed populations in field areas using these GM and non-GM crops. In addition, growing GM herbicide-tolerant crops could provide farmers with the flexibility to improve plant diversity by only controlling weeds when they are competing with the crop."
Chairman of the Bright project management committee, Windsor Griffiths, said: "The Bright report will benefit Government policy makers not just in Britain but across Europe.
"This four-year research project has shown clearly the benefits and limitations of GM herbicide-tolerant crops when grown in rotation with non-GM crops.
"The knowledge we have accumulated will be very useful for providing guidance for growers of these crops, should they be commercialised."Reuse content