Meanwhile, a battle rages to stop our fields turning into 'green concrete'

There has been a chorus of criticism throughout the spring and summer, there have been meetings of anxious locals in parish halls, there have been farmers who have changed their minds, sometimes under pressure, and there have been attacks on fields across the country, yet the Government announced yesterday it was pressing on with its controversial programme of farm-scale trials of GM crops.

There has been a chorus of criticism throughout the spring and summer, there have been meetings of anxious locals in parish halls, there have been farmers who have changed their minds, sometimes under pressure, and there have been attacks on fields across the country, yet the Government announced yesterday it was pressing on with its controversial programme of farm-scale trials of GM crops.

But the hostility of the green activists, and the Government's unwavering decision to press on, mark a genuine, profound and honestly held disagreement about the trials' value.

The four-year test programme has nothing to do with food safety: it is designed to test the effects on wildlife of the weedkillers the GM crops have been bred to tolerate, which are "broad spectrum" herbicides: they kill virtually everything they come into contact with.

The idea of the agrochemical companies, such as the German firm Aventis, is simple: farmers get rid of all their weeds and get a much higher crop yield. But this may well mean getting rid of everything else in the field apart from the crop, and turning the countryside into "green concrete".

It was the Government's wildlife advisers, English Nature, who first wanted the trials and called loudly for a four-year moratorium on the commercial growing of GM crops. Tony Blair, a GM enthusiast, publicly ruled out any official ban, but in one of the deftest political moves of the current administration, the Environment minister Michael Meacher persuaded the GM companies to bring in a moratorium voluntarily.

The point of the trials, as Mr Meacher never tires of pointing out, is to gather solid scientific information that may well prevent GM crops being grown commercially in the United Kingdom, ever. People who disrupt them, he says, are shooting themselves in the foot.

Yet for the more radical pressure groups, such as Greenpeace and Friends of the Earth (FoE), any value the trials might eventually have is outweighed by the immediate threat of releasing GM genes into the countryside.

Their opposition is coloured by their hostility to the big companies which, often ruthlessly, have promoted GM technology - Monsanto above all - but they also have science on their side.

While separation distances have been set for the trials, a report commissioned last year by the Government itself from the John Innes Centre in Norwich, Europe's leading GM research institute, found that contamination of other plants by either pollen or seed cannot be "entirely eliminated", whatever the distance between crops.

Both bees and the wind can carry pollen several miles, while seeds from oilseed rape could be accidentally dispersed during harvesting or transferred to fields from machinery, the report found. Crucially, it also found that the buffer zones, set at 200 metres for oilseed rape, would have to be increased, especially if the organic farming industry is to maintain its "GM-free" certification.

The radical pressure groups have won some notable victories. Of the 66 farmers who agreed to host trial sites this spring, 18 dropped out, usually after loud local opposition. In West Portholland, Cornwall, the farmer's milk buyer was not happy to take milk if the farm was growing GM crops.

In Ainderby Steeple, North Yorkshire, beekeepers feared honey might be contaminated. In Tittleshall, Norfolk, a parish meeting voted 94-4 against the trial continuing, while in St Osyth, Essex, a parish referendum went against the farmer. There have been 10 attacks on sites this year, mostly by local people.

So the trials go on, but the problem of separation distances remains. If the Government does find that the Advanta seeds were contaminated over a distance of four kilometres, how can it then set its separation distances at any less? But with those intervals, officials admitted yesterday, it would be virtually impossible to find trial sites, and the programme would collapse.

Tough one, eh, Michael? Wrestle with it on holiday. That's what we pay our politicians for.