Mr Kennedy urged the Government to respond to "enormous" public concern about the technology and impose a five-year moratorium on the growing of GM crops for commercial release.
Unveiling his party's new policy paper on the controversial science, he warned that current field-scale trials posed a risk to nearby farms through cross-pollination.
To protect organic and other non-GM crops in neighbouring fields, the trials should be subject to much bigger isolation distances and be monitored by independent assessors rather than the biotech companies running the experiments, Mr Kennedy said. Both biotech firms and regulatory bodies should also be made legally liable for any damage to people or the environment caused by the crops.
Firms such as Monsanto and AgrEvo, the two leading GM companies, would have to pay full compensation, possibly millions of pounds, if found guilty of negligence, the Liberal policy indicates. Mr Kennedy, who visited one of the GM trial sites yesterday, said that it was time the Government ordered a major overhaul of the regulations governing trials.
"The Government must realise that public concern on this issue is enormous. By ignoring these concerns they risk alienating a large section of society and causing long-term environmental damage," he said. Asked if he supported the recent Greenpeace action in destroying GM trial crops, he said: "We as Liberal Democrats always support the right to express civil disobedience in a peaceful way. What we don't recognise is the right to go into other people's property and to begin to destroy it."
Dr Jack Cunningham, the Cabinet "enforcer", claimed the issues raised were already being dealt with. "The UK regulations and tests are the most rigorous in the world," he said. "The UK is the only country in the world investigating the environmental impact of growing GM crops at this level of detail and thoroughness."
n Britain faces a food poisoning epidemic of "cataclysmic" proportions unless farmers reduce the number of antibiotics in livestock, the Advisory Committee on Microbial Safety of Food warned yesterday.