As GM crops in the UK undergo their final tier of farm-scale trials, a new report raises doubts about their long-term economic viability.

A study by the Soil Association suggests that GM crops have been an "economic disaster" in North America, costing £8bn (US$12.3bn) in lost profits and higher subsidies since 1999.

Seeds of Doubt, the new Soil Association study, claims that farmers reported lower yield, continued reliance on chemical sprays and, perhaps most worryingly, widespread contamination of non-GM and organic crops.

This has in turn damaged exports. The report claims that around £400m a year has been "wasted" after almost the entire North American export volume of maize and rape to the European Union was lost following the introduction of GM varieties.

For further information on this study click here.