By Alex Kirby
BBC News Online environment correspondent
Both sides in the UK's increasingly polarised debate over genetically modified crops have been accused of misrepresenting recent research results.
A GM spring rape was one of those tested
Lord May, president of the Royal Society, says opponents and supporters of GM spun the outcome of farm-scale trials to suit their own arguments.
He says the research data should have prompted a debate on farming's future.
The trials data, published in October, revealed new weedkiller-tolerant crops had mixed effects on country wildlife.
GM beet and rape fields were found to fare worse than in the conventional control plots.
In contrast, wild creatures in GM maize fields seemed to do better than with conventional plants, though the validity of that test was questioned by critics.
Lord May said some members of both the biotech industry and environmental campaigns had represented the results "in a biased and selective way".
He said: "The experiments demonstrated that GM crop technology may be applied in ways that are better for biodiversity than conventional practices, or alternatively may be used to further intensify agriculture with a corresponding negative effect on farmland wildlife.
"To generalise and declare 'all GM is bad' or 'all GM is good' for the environment as a result of these experiments is a gross over-simplification, but statements from both sides in the GM propaganda war have claimed 'victory' based on these findings.
"Rather than closing the case for or against GM crops, these results should drive society to ask more questions, not just about GM crops, but about agriculture more generally.
"They should be used as a catalyst for a debate about the future of modern agriculture."
Lord May was speaking before the Royal Society, the UK's national academy of sciences, submitted evidence on the implications of the farm-scale evaluations to the government advisory body, the Advisory Committee on Releases to the Environment (Acre).
One at a time
The society believes "it is not the technology of genetic modification but the weed management system associated with it, such as volumes of herbicides used and their persistence, which determines the effect on biodiversity of a particular agricultural system.
"The different impacts of the GM crops on farmland wildlife are not a result of the way in which the crops have been genetically modified."
In its evidence the Royal Society says there could be different ways of managing these crops which might reduce their harmful effects on wildlife.
This, it says, reinforces the importance of evaluating GM crops on a case-by base basis.
Lord May said: "The most pressing question arising from the evaluations is not whether GM plants are better or worse for the environment than conventional crops, but instead what type of modern agriculture we want...
"If appropriately developed, GM crops could be used deliberately to improve the environment. But first, much larger questions need to be answered about the kind of world we want to live in.
"Social and environmental choices about agricultural practices and their impact need to be made before we look to science and technology to help provide the solution.
"But if it chooses, society could use these results to persuade companies to produce crops that are better for the environment."