Environment Secretary Margaret Beckett said that following three-year long trials the government approved in principle the growing of an herbicide-tolerant maize.
She said the maize crop, produced by Cropscience, the British arm of German biotech company Bayer, probably would not be grown commercially in Britain until spring next year at the earliest.
Beckett added that the government opposed the commercial cultivation of varieties of GM beet and oilseed rape, which fared badly in the trials.
The issue is a sensitive one for the government. Opinion polls have found a majority of the public opposed to such crops — labeled "Frankenstein foods" by some tabloid newspapers.
Beckett insisted that the maize crop must be grown under the same conditions as the trials "or under such conditions as will not result in adverse effects on the environment."
She also stressed that commercial growers must carry out further scientific analysis. Before commercial cultivation can proceed, "separate approval will also be required under seeds legislation and also under pesticides legislation for the associated herbicide use," she added.
Addressing the House of Commons, Beckett said the government would assist farmers who wanted to set up GM-free zones.
"Safety, human health and the environment must remain at the heart of our regulatory regime and rigorous and robust monitoring must be maintained," she added.
No commercial GM crops are currently grown in Britain, but the government has conducted crop trials, scientific reviews and cost-benefit studies.
British scientists concluded in October that growing herbicide-tolerant maize under trial conditions had no adverse impact on surrounding plants and wildlife.
During the three-year-long study, scientists grew GM crops and traditional crops side by side, using different weedkillers on each, and monitored wildlife in the fields.
GM oilseed rape and beet cultivation, under the specific conditions set up for the trial, were judged to have an adverse impact on the environment, but the GM maize did not.
Environmental groups at the time criticized the maize study. They said the use of the highly toxic weed-killer Atrazine on the conventional crops had biased the results in favor the GM maize, on which a gentler herbicide was used.
Earlier this month, a legislative committee said the trials were "unsatisfactory" and noted that Atrazine is being phased out in Europe.
Beckett said Tuesday that commercial growers of the GM maize must carry out further research on the implications of the weedkiller being phased out.
The announcement came as the British Medical Association said GM foods were highly unlikely to damage human health.
"Our assessment of all the available research is that there is very little potential for GM foods to cause harmful health effects," said David Carter, chairman of the BMA's science board.
However, he said more research and surveillance was needed to allay public concerns and provide convincing evidence of the benefits of growing GM crops.
Tony Juniper, director of Friends of the Earth, called on the government to change its mind.
"Tony Blair must not ignore the threat GM poses to our food, farming and the environment," he said.
Decisions on whether to permit the cultivation of GM crops in the European Union are taken collectively by member states after a thorough assessment of the crop concerned. It is ultimately up to each government whether the crop is grown in its country.
The European Union approved the maize crop in April 1998, a few months before introducing a moratorium on new biotech foods. The EU is currently divided over whether to lift its 5-year-old moratorium.
Spain is the only EU country to plant significant amounts of biotech crops, with 32,000 hectares of biotech corn last year, up a third from 2002.