"Farmers should remain free to decide not to grow GM crops," EU Environment Commissioner Stavros Dimas said at the two-day conference in Vienna.

"But that choice is eroded if GM and non-GM crops are unintentionally mixed up," added Agriculture Commissioner Mariann Fischer Boel, saying it was important to ensure "that GM and non-GM crops are properly segregated."

Non-governmental organisations said however such segregation was impossible and GMOs should be banned altogether.

"If GMOs are grown, conventional and biological agriculture are bound to be contaminated," Eric Gall, EU policy director for environmental group Greenpeace, told AFP.

He argued long-term risks related to GMOs were still unknown and contamination would generate financial losses for farmers of non-GM crops, with no possibility of compensation by industries and GMO growers.

NGOs seek an EU-wide policy against GMOs while the European Union delegates these matters to member states.

"We do not think it would be helpful to propose binding EU-wide rules on co-existence at present," Fischer-Boel said, since co-existence measures vary according to geography or climate.

An estimated 2,000 protesters, according to police, from all around Europe, marched to the Congress Centre where the conference was being held and handed the EU Commissioners a "Vienna Declaration," calling for a GMO-free Europe.

Austrian Agriculture Minister Josef Proell told them: "Europe is listening. We have very similar interests on the issue of genetic engineering."

But protesters were less hopeful. "Actually, we do not expect any result from inside," one protester, Renate Griletz, said, "but they should know we are standing here and are against it."

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