Two "citizen's juries" have said the moratorium on the use of genetically modified crops in the UK should continue.
GM crops have attracted widespread opposition
The juries, made up of 30 members of the public, said the possible health and environmental impact of GM crops were still such a concern that commercial planting should not yet go ahead.
Their feelings were published in the People's Report on GM Crops, compiled after the jurors spent six weeks hearing expert evidence.
The report was funded jointly by the Consumers' Association, Greenpeace, the Co-operative Group and Unilever.
The juries heard expert witnesses discussing the impact of GM crops on farming and the environment; food safety; potential health effects and the government's handling of the issue.
At the moment, the biotechnology industry has agreed a voluntary moratorium on submitting applications to grow GM crops until the results of three-year farm-scale studies are unveiled - probably in October.
The juries called for the moratorium on commercial planting of GM crops to continue.
They also urged the government to carry on for the long term with testing GM crops in fields.
The two 15-person juries were held simultaneously in Newcastle upon Tyne and St Albans, Hertfordshire.
Helen Colclough, a juror from the Newcastle group, said: "We believe that the implications of GM technology are not yet fully understood and have not been adequately shared with the public.
"The jury felt because of this we could not justify an unqualified green light to GM crops being grown in the UK."
Vinay Thoree, on the St Albans jury, said: "There is a general misconception that GM food will lead to human mutations.
"However, the attempts by manufacturers of GM technology to persuade us that the UK will lose out if we do not embrace GM is disingenuous.
"Evidence shows that the GM crops currently on the market offer little
benefit to consumers, the environment or the Third World.
"If the UK and developing countries really want to gain from GM then industry must develop products that will do more than line the pockets of the manufacturers who produce it."
As far as food was concerned, the jurors felt not enough was known about the potential health effects of GM food for them to be on sale.
None of the jurors had heard of the government's GM Nation debate before they participated in the juries, despite the process being launched several weeks beforehand, the report said.