The debate over genetically modified – or GM – crops has reached a new level of complexity in Britain, as environmentalists exploit the sensitivity of food retailers to food-safety issues.

Recently, a prominent member of Greenpeace announced that Tesco, Britain's largest food retailer, would no longer accept fruit and vegetables grown on land previously used for GM crops.

The notion that genetically modified material from a previous crop could somehow be a food-safety concern is absurd and Tesco admits there's no scientific basis for it. But British food retailers know it's critical to be squeaky clean on the issue of genetically modified food. Perceptions are what matters.

In fact, Tesco’s curfew on produce grown on GM field trial land, the only GM cropping in the UK, is for one year, not indefinite as was implied by Greenpeace. So while the company was quick to make this clear to its suppliers, it didn't make too much of this clarification. After all, why spoil the goods news of ‘Tesco reacts to consumers’ concerns.’

Of course, this probably leaves some people with the impression that growing a GM crop can somehow permanently pollute the soil.

Because consumer perceptions are most certainly fed by the behaviour of food retailers, opposition to genetic engineering will not be overcome easily. 

This unholy alliance of environmentalists and food retailers is likely to be broken only if an emotional issue can be brought to the rescue of science. The most likely candidate is the humanitarian one – that this technology can be used to help the developing world. 

Much of the activist motivation against genetic engineering appears to stem from knee-jerk reaction to American capitalist domination. With this cause removed, opposition might be more rational and science more telling.

For CBC commentary, I'm David Walker, an agricultural economist, at Lodge Farm Postwick in Broadland Norfolk, England.