Organic lobbyists pulled off a coup this week when they enlisted Peter Ainsworth, the shadow secretary of state for the environment, to their campaign against cultivation of GM crops in the UK.

Ainsworth, MP for Surrey East, has pledged to take their case ­- and a delegation of organic producers ­- to David Miliband, secretary of state for the environment. A meeting is likely to take place within two months.

Representatives of 74 organic businesses told Ainsworth this week they feared government moves to allow non-GM foods to contain up to 0.9% GM content would result in an added cost burden on organic producers. The upper limit would form part of 'co-existence' rules, designed to regulate the growing of GM food in the UK alongside non-GM.

Experts warn that if GM crops are grown here, some tainting of non-GM crops with GM is inevitable - and the EU has left member states to draw up national limits on GM content for non-GM foods.

In a consultation last year - the results of which are still awaited - the UK government proposed following a non-binding European Commission opinion allowing a GM content of up to 0.9% in non-GM foods.

This means that if GM content of up to 0.9% is there by accident, for instance through cross-pollination, a product does not have to be labelled GM.

However, organic certification bodies demand in their standards a GM content of no more than 0.1% in all organic products ­- and they have warned they will stick with that, whatever the government decides.

This means that, if the government does opt for a 0.9% co-existence limit, the responsibility for ensuring crops stay GM-free will lie squarely with organic producers - or they face losing their organic status.

"This tells you where the economic burden will fall," said Soil Association director Peter Melchett, who attended the meeting with Ainsworth.