The UK's department for the environment, food and rural affairs (Defra), which originally gave approval in December for BASF to undertake research trials of a GM potato at two sites in England, one in Cambridgeshire and the other in Derbyshire, said that it would now consider BASF's proposal as a new application in accordance with the Genetically Modified Organisms (Deliberate Release) Regulations 2002.

The issue has again brought into sharp relief the division within Europe over GM food.

Defra said in December that it was satisfied that the trials would not result in any adverse effect on human health or the environment, but environmentalists claim that the risk of contamination of the food chain means that the trails are unnecessary and uncalled for.

"These GM trials pose a significant contamination threat to future potato crops," said Friends of the Earth GM campaigner Clare Oxborrow.

"We don't need GM potatoes and there is no consumer demand for them. The government should promote safe and sustainable agriculture, not this half-baked GM potato plan."

Friends of the Earth claims that BASF applied to trial the GM potatoes in Ireland last year, but pulled out because of the strict conditions imposed by the Irish authorities. It says that the conditions imposed by Defra are not as strict and could lead to GM contamination of the food chain.

But BASF believes that the trials are not only safe, but could lead to a number of advantages. The GM potato has been developed for resistance to late potato blight, a significant disease problem for potato growers that they normally combat by using chemical fungicides.

The trials are designed to test the effectiveness of the potato's resistance against UK strains of the disease. Similar trials are already underway in Sweden, Germany and the Netherlands.

The issue of GM approval within the EU is one of the most contentious in agriculture. The recent announcement that US authorities had traced amounts of unapproved genetically modified (GM) food in samples of rice prompted the EU to clamp down on all imports from the US.

The immediacy of this action illustrated the stringent controls the EU has in place to guard against unauthorised products entering the food chain, and also reflected consumer fears over the technology.

In this particular case, the Advisory Committee on Releases to the Environment (ACRE), which has already made an initial assessment on the proposed change in location, has provisionally concluded that it does not affect its earlier opinion that the trials do not raise any safety concerns for human health and the environment.

But before reaching a definitive decision, Defra said that it would consider any representations that people may wish to make about the risk of environmental damage posed by the GM trial.

The deadline for representations is 20 April 2007.