The commercial growing of genetically modified crops would bring little short-term benefit to the British economy, a government report has said.
The first of three major reports into biotech plants says only a narrow range of existing GM crops is suited to British conditions.
GM crop trials have proved highly controversial
The report from the Cabinet Office Strategy Unit says the lack of demand for the GM foods from shoppers is likely to limit the extent to which farmers grow the controversial new varieties.
But in a signal that Britain should not turn its back on GM technology, it argues future GM crops could offer wide ranging benefits to both farmers and consumers in the longer term.
Those potential plus points include GM crops more suited to the British farming climate and direct health benefits, such as foods with added nutrients.
"However, the overall balance of future costs and benefits will depend on public attitudes, and on the ability of the regulatory system to manage uncertainties," it adds.
The government is set to make a decision later this year on whether or not GM crops should be commercially grown.
It is seeking public opinion on the issue and has launched a website allowing people to have their say in the GM debate, which ends on 18 July.
Meanwhile, the results of three-year farm-scale GM crop trials are due in the autumn.
The study for Friday's report looked at the impacts of GM food and farming on farmers, processors, retailers and consumers, including organic farmers.
It also considered the environmental impacts of GM crops, and looked at the biotechnology industry.
The report suggests the signal sent out by the government's decision on GM could affect the UK's ability to attract investment from science-based industries.
Environment group Friends of the Earth (FoE) has warned that allowing the large-scale growth of GM crops, like oil seed rape, would almost certainly lead to widespread contamination of organic plants.
The report says the rules imposed on growing GM crops will determine whether the cost of producing and segregating them from organic plants would outweigh any financial gain.
"Future decisions on GM crops will involve trade-offs between costs in one area and benefits in another," it says.
Another example of that trade-off is the fact that strict regulations can reduce risks but also discourage development and farming of GM crops, it argues.
Environment Minister Elliott Morley said: "The report highlights that GM crops are one area in which GM technology has significant potential to contribute to the UK's future economic prosperity and sustainability.
"But it also points out that GM crops are just one possible tool for achieving our goals - important advances in crop production will also come from conventional and organic techniques."
Mr Morley told BBC Radio 4's World At One that an open mind should be kept about GM crops.
But there are "a lot of hurdles" before ministers could even consider giving the go-ahead for commercial GM farming, he added.
Mr Morley's predecessor as environment minister, Michael Meacher, said government should not approve GM crops in the face of the evidence.
Mr Meacher said: "There is absolutely nothing wrong in pursuing biotechnology in terms of what may be future gains.
"But that is totally different from giving a positive decision about commercialising GM crops now, when there is such powerful
opposition within the country."
Peter Melchett, policy director of the Soil Association, said the report marked a huge shift in the government's position.
"The government spin on the report suggests it promises GM jam tomorrow," he said.
"But in reality it honestly and openly acknowledges that things are just as
likely to go wrong for GM in future as they are to go right."
Earlier, Tony Combes, of the Agriculture and Biotechnology Council, told the BBC it had been "proved throughout the world" that GM crops gave higher yields for lower costs.
But Canada's National Farmers Union president Stewart Wells said that in his experience, GM crops had failed to live up to their promises of increased yields and reduced costs.