GM crops could be potentially harmful to the environment, scientific trials ordered by the government have found.

Campaigners against GM food claimed victory after the scientific trials indicated there could be significant impact on biodiversity.

The results found some types of GM crops require less herbicide than conventional crops but others required more.

Andrew George, rural affairs spokesman, said: "The government cannot give the go-ahead for GM crops in the UK on the basis of this report.

"Every step of the way, official research has shown the public need much more reassurance.

"No responsible government would permit the commercial planting of GM crops under current circumstances.

"The public doesn't want it, supermarkets won't stock the stuff, there are major environmental concerns and there are no benefits to our farmers.

"The question must now be - why on earth would the government say 'Yes' to GMs?"

David Lidington, shadow environment secretary, said: "The evidence published today would not justify a decision to authorise the commercial growing of GM crops.

"These results deserve careful study. I shall want to hear the views of other scientists on the findings published by their professional peers.

"The fact that the impact of different GM seeds on wild plants and invertebrates varies so markedly shows that we must proceed with scepticism and caution. There should be no blanket approval. Any variety of GM seed proposed for licensing should be subjected to rigorous field trials and risk analysis.

"In two instances, GM sugar beet and rape, the evidence clearly suggests that commercial cultivation would cause environmental harm.

"Although the results for GM maize indicate environmental benefits, that conclusion depends at least in part on the effectiveness of the herbicide used to kill weeds in the control crop.

"The recent EU ban on atrazine has thrown doubt on the validity of the maize trials. This issue needs to be addressed through further scientific debate and, possibly, a new round of crop trials.

"Other serious issues like the risk of cross-pollination to organic and other non-GM crops and liability for any harm found to have been caused by GM were not addressed at all in these farm-scale tests.

"The government needs to resolve these issues too before any decision to authorise commercial GM crops in Britain.

"Policy on GM needs to be driven by reliable scientific evidence and a rounded consideration of our national interest."

Forum Response: National Farmers Union

Sir Ben Gill, president of the NFU, said: "The NFU has been a supporter of the farm scale trials because we believe it is important to look at all the evidence. We are pleased the initial results have now been published.

"Praise should be given to all those farmers involved in these important trials."The NFU recognises there may be potential benefits to farmers, the environment and wider society from GM technology. But we also recognise that there are serious public concerns.

"The decision on whether to allow these crops to be grown commercially now lies with the government and it must be done on a case by case basis using all the available evidence, including these trials, to make its decision."

Forum Response: Consumers' Association

Monique Warnock, campaign team leader at the Consumers' Association, said: "Today's results have confirmed our concerns that commercialisation of GM crops in the UK, will destroy consumer choice once and for all.

"The GM crops evaluated cannot exist side by side with conventional crops without contamination.

"This means that despite only 32 per cent of consumers being in favour of GM commercialisation in the UK, consumers who do have concerns will be left with no choice.

"Each and every exercise the government has carried out to help inform its decision on commercialisation of GM has shown that the UK is just not ready.

"The government must not bow to industry pressure. Instead it must carry out more research on the effects on human health and the environment.

"While some consumers believe that GM does have the potential to offer consumer benefits, these benefits are clearly some way off.

"There should be no GM products on the market until the government has addressed the environmental concerns highlighted today and the many other outstanding consumer concerns over the use of this technology."