London

After years of careful deliberation, the British government this week took a crucial step towards acceptance of genetically modified crops.

On 9 March, government ministers announced limited approval for commercial planting of a maize (corn) variety engineered to be resistant to a specific herbicide — the first such approval in Britain.

Although the approval lasts only until 2006, the decision indicates that prime minister Tony Blair's government is willing to support transgenic technology in the face of widespread public opposition. In Britain, opposition to agricultural biotechnology has been early and strident. Both supporters and enemies believe this week's decision will influence debates outside Britain about transgenic crops (see "Californian county bans transgenic crops").

Environment minister Margaret Beckett announced that farmers can grow the maize if they follow management guidelines used in farm-scale studies of the crop's environmental impact. These studies found that the maize could have a beneficial effect on biodiversity, provided the timing and nature of herbicide spraying are carefully controlled (see Nature 425, 751; 2003).

Blair's government has generally backed the technology since coming into office in 1997, but it has been cautious about allowing commercial cultivation. Opinion polls show that the public is concerned about the impact of the crops on human health and the environment, and environmental groups have campaigned against the technology.

The case for the crops was boosted by a scientific review, released last July, which found no reason to rule out carefully managed cultivation of the plants. The review was discussed at a cabinet meeting last month. Leaked minutes of the meeting state that ministers acknowledged public opposition, but thought that it “might eventually be worn down by solid, authoritative scientific argument”.

Despite this week's announcement, the company marketing the maize used in the farm-scale study — Bayer CropScience, based in Monheim am Rhein, Germany — is unlikely to sell many seeds in Britain in the near future. The maize has had European Union approval since 1997, but the terms of the approval will have to be modified to take the herbicide restrictions into account before sales can start. Officials in Beckett's department say this will take several months, although they predict that the necessary rules will be in place for farmers to plant transgenic maize in spring 2005. Farmers will, however, be keeping a nervous eye on the first plantings, as environmental activists have damaged several research plots.

Farmers will also be wary of planting genetically modified varieties before the government has clarified rules governing how they should be kept separate from nearby conventional crops. In addition, European Union approval for the maize will have to be renewed if cultivation is to extend beyond 2006.

Renewing the application may not be a formality. The farm-scale trials compared transgenic maize with conventional varieties that had been treated predominantly with triazine herbicides, powerful weed-killers that are likely to be banned in Europe by 2006. When compared with fields treated with less intense herbicides, the biodiversity benefits associated with transgenic maize decrease by around a third, according to a study led Joe Perry, a statistician at Rothamsted Research, an agricultural research firm based north of London (see J. N. Perry et al. Nature doi:10.1038/nature02374; 2004).