Some fear that genes inserted into crops to confer new traits could escape into the wild, or even affect human health in unpredictable ways.
They suspect that the long-term experiments necessary to assess the risks have not been carried out.
"I see worries in the fact that we have the power to manipulate genes in ways that would be improbable or impossible through conventional evolution," said Colin Blakemore, Waynflete professor of physiology at Oxford University and president of the British Association for the Advancement of Science.
"We shouldn't be complacent in thinking that we can predict the results."
Gordon McVie, head of the Cancer Research Campaign, is also concerned: ''We don't know what ... genetic abnormalities might be incorporated into the genome [the individual's DNA].
"I'm more worried about humans than about the environment, to be honest. One of the problems is that because it's a long-term thing, you need to do long-term experiments."
David Bellamy, the botanist, condemned the commercial motives behind the "gene revolution". It would "disenfranchise poor people from their genetic inheritance and their lands", and he warned: "Supercrops and superweeds know no boundaries."
The Independent spoke to a broad range of scientists from a variety of disciplines, including biology, physics and astronomy, to ask them if they eat GM foods; if they have any concerns about GM foods and crops; and if they think the public is being well-informed.
The inquiries followed a letter published in The Independent on Friday from Richard Dawkins, the Oxford evolutionary scientist, who condemned "ignorant hysteria over scientific matters" that led many people to question the safety of transgenic products.
But The Independent's survey reveals that prominent scientists are not convinced that biotechnology firms are completely in control of their products. "I have concerns about the long-term environmental effects of these crops," said Susan Greenfield, a leading brain researcher at Oxford University.
The Astronomer Royal, Sir Martin Rees, said: "Although I would eat them, I think one should have some concerns."
Tom Kirkwood, professor of biological gerontology at Manchester University, would eat genetically modified food, but with reservations. ''I don't think GM food would be toxic, but I do have concerns about gene transfer...to other plants. I think the risks are not being properly assessed,'' he said.
John Sumpter, professor of biology at Brunel University and an expert on chemicals in the environment that mimic female hormones, is also concerned about the risks to wildlife. "Eating GM food probably would not worry me a great deal. My concerns are about what would happen when GM crops escape from fields - which they will do.''
Richard Horton, editor of The Lancet, said: "I think these should have proper safety testing - like a drug - on animals, and then on humans."
Steve Jones, professor of genetics at University College London, said: "Nothing in life is ever safe, but compared to other things we have to worry about - bacteria and BSE, say - the risks are tiny."
The most assured response came from Dr Keith McCullagh, chief executive of British Biotech, the pharmaceuticals company. "There is no scientific basis for any hazard being present in these foods," he said. "The way in which they (GM foods) have been modified doesn't introduce any new hazard to human health."
The Women's Nutritional Advisory Service, which is opposed to GM food, has named 20 suppliers and retailers that actively use GM products - including Sainsbury's, Safeway, Somerfield, Tesco, Asda, Budgens, Kwik Save and Spar. It also lists 47 firms that avoid genetically modified soya - the most widely used GM food - including Waitrose and Iceland.
Watchdog sought, page 13
How the Experts Assess Genetically modified food
'We have the power to manipulate genes in ways that would be impossible through evolution'
'Gene revolution [would] disenfranchise poor people from their genetic inheritance and their lands'
'Nothing in life is ever safe, but compared to other things we have to worry about ... the risks are tiny'
'The way in which GM foods have been modified doesn't introduce any new hazard to human health'Reuse content