Yet another nail was hammered into the coffin of the GM food industry in Britain yesterday when the final trial of a four-year series of experiments found, once more, that genetically modified crops can be harmful to wildlife.
The study was the fourth in a series that has, in effect, sealed the fate of GM in the UK - at least in the foreseeable future. They showed the ultra-powerful weedkillers that the crops are engineered to tolerate would bring about further damage to a countryside already devastated by intensive farming.
Only one of the four farm-scale trials, which have gone on for nearly five years, showed that growing GM crops might be less harmful to birds, flowers and insects than the non-GM equivalent - and even that was attacked as flawed, because the weedkiller the particular conventional crop required was so destructive it was about to be banned by the EU.
Even so, a year ago the Government gave a licence for that crop - a maize known as Chardon LL, created by the German chemical group Bayer - to be grown in Britain, thus officially opening the way for the GM era in Britain, to loud protests from environmentalists.
However, only three weeks later Bayer withdrew its application, suggesting the regulatory climate would be too inhibiting. That followed the withdrawal from Europe of the world leader in GM crops, the American biotech giant Monsanto, which also seemed to have tired of the struggle.
Since then, the GM industry in Britain has withered on the vine, despite the fact that some members of the Government, and Tony Blair in particular, were privately great supporters of it from the outset. Official policy is portrayed as being neutral and based simply on scientific advice.
But yesterday's results make it even less likely that other big agribusiness firms will want to come forward and go through the extensive testing process - and public opposition - that bringing a GM crop to market in Britain would involve.
Last night, the Conservatives spotted a political opportunity from the latest test results and, this morning, the shadow Environment Secretary, Tim Yeo, will pledge to prevent any commercial planting of GM crops until science showed it would be safe for people and the environment, and there was a liability regime in place to deal with any cross-contamination.
Observers saw that as yet another Tory attempt to win over Middle England voters in the pre-election campaign.
The fourth and final mass experiment involving GM crops has found that they caused significant harm to wild flowers, butterflies, bees and probably songbirds. Results of the farm-scale trial of winter-sown oilseed rape raised further doubts about whether GM crops can ever be grown in Britain without causing further damage to the nation's wildlife.
Although the experiment did not look directly at the catastrophic demise of farmland birds over the past 50 years, ornithologists said the results suggested that growing GM oilseed rape would almost certainly exacerbate the problem.
David Gibbons, the head of conservation at the Royal Society for the Protection of Birds, said the herbicides used to spray GM rape killed broad-leaved wild flowers such as chickweed and fat hen which are important to the diet of songbirds such as skylarks, tree sparrows and bullfinches.
"For most farmland birds, broad-leaved weeds are a particularly important part of their diet. There are a few birds that will take grass seeds but, by and large, it would be hard to see how the loss of broad-leaved weeds would be beneficial to them," Dr Gibbons said. "Broad-leaved weeds are particularly important to farmland birds and the widespread cultivation of this crop, in this way, would damage hopes of reversing their decline."
The trial of winter oilseed rape involved planting conventional and GM forms of the crop in adjacent plots at 65 sites across Britain. Scientists then carefully monitored wild flowers, grasses, seeds, bees, butterflies and other invertebrates. Over the course of the three-year experiment, the scientists counted a million weeds, two million insects and made 7,000 field trips. Although they found similar overall numbers of weeds in the two types of crop, broad-leaved weeds such as chickweed were far fewer in the GM plots. The scientists counted fewer bees and butterflies in the GM plots compared to plots of conventional oilseed rape.
Les Firbank, of the Centre for Ecology and Hydrology in Lancaster, who led the study, said that there was about one-third fewer seeds from broad-leaved flowers in the GM plots compared to fields with conventional oilseed rape.
"These differences were still present two years after the crop had been sown ... So we've got a significant biological difference that is carrying on from season to season," he said.
GM oilseed rape is genetically designed to be resistant to a weedkiller that would kill the non-GM crop. It means that farmers are free to use broader-spectrum herbicides.
The three previous farm-scale trials into crops investigated spring-sown oilseed rape, maize and beet. These showed that growing GM rape and GM beet did more harm to wildlife than their conventional counterparts.
"All of the evidence that we've got from the farm-scale evaluations points out that differences between the treatments are due to the herbicides. It's the nature of the chemicals and the timing at which the farming is done," Dr Firbank said.
Christopher Pollock, chairman of the scientific steering committee that oversaw the farm-scale trials, said: "What's good for the farmer is not always good for the natural populations of weeds, insects, birds and butterflies that share that space."
Farm-scale trials of GM crops are unique to Britain and represent the first time that scientists have evaluated the environmental impact of a new farming practice before it has been introduced, Professor Pollock said. Results of the latest trial are published in Proceedings of the Royal Society B .
The Four Tests
Test 1: Spring-sown oilseed rape, October 2003
Nationwide tests found that biotech oilseed rape sown in the spring could be more harmful to many groups of wildlife than their conventional equivalent. There were fewer butterflies among modified crops, due to there being less weeds. Verdict: GM fails.
Test 2: Sugar beet, October 2003
The GM crop was found to be potentially more harmful to its environment than crops that were unmodified. Bees and butterflies were recorded more frequently around conventional crops, due to greater numbers of weeds. Verdict: GM fails.
Test 3: Maize, October 2003
The production of biotech maize was shown to be kinder to other plants and animals compared to conventional crops. More weeds grew around the biotech maize crops, attracting more butterflies, bees and weed seeds. Verdict: GM passes, but critics brand study as flawed.
Test 4: Winter-sown oilseed rape, March 2005
Tests showed that fields sown with the biotech crop had fewer broad-leaved weeds growing in them. This impacted on the numbers of bees and butterflies, which feed on such weeds. Verdict: GM fails.
HALF A CENTURY OF DEBATE
1953: James Watson and Francis Crick unravel double-helix form of DNA, making biotechnology a possibility.
1983: Kary Mullis, a scientist and surfer from California, discovers the polymerase chain-reaction which allows tiny pieces of DNA to be replicated rapidly. Shortly after, US patents to produce GM plants are awarded to companies. US Environment Protection Agency approves release of first GM crop: virus-resistant tobacco.
1987: Potato becomes first GM plant introduced to UK.
1994: Flavr Savr tomato is approved by US Food and Drug Administration, paving way for more GM products.
1997: Public find Monsanto GM soya is used, unlabelled, in processed UK food.
June 1998: The Prince of Wales stokes debate by saying he will neither eat GM produce nor serve it to his family or friends.
July 1998: English Nature, the Government's wildlife advisory body, calls for a moratorium on planting of GM crops while trials are conducted into effects on wildlife of their weedkillers.
February 1999: Michael Meacher, the environment minister, persuades GM companies to agree to a moratorium until farm-scale weedkiller trials are done.
Spring 2000: Farm-scale trials of GM crops begin.
October 2003: Preliminary results find that two of three GM crops are believed to damage the environment.
March 2004: Cabinet members approve qualified planting of first UK GM crop.