PARIS - Hundreds of activists marched in Paris on Tuesday ahead of the expected approval of a law they say blurs the line between natural and genetically modified (GM) foods.

The bill lays down conditions for the cultivation of GM crops in France, Europe's largest grain producer and exporter, and creates a body to oversee GMO use. The vote is due to take place late on Tuesday or on Wednesday. Protesters, some wearing yellow hats in the shape of maize cobs and others dressed in white suits imitating scientists, gathered near the National Assembly to voice their opposition.

"We must give consumers the choice of eating quality products, with or without GMO," said Jean Terlon, cook at the restaurant Le Saint-Pierre in Longjumeau, close to Paris.

While GM crops are common in the United States and Latin America, France and many other European countries are dubious about using the new genetic technology in agriculture. France banned the sole GM crop grown in the European Union, a maize (corn) developed by U.S. biotech giant Monsanto, in February because it had serious doubts about whether it was safe for the environment. GMO cultivation is still legal, however. The new French law, which would implement a European Union directive adopted in 2001, sets the rules a farmer has to respect to grow GM crops. These include limiting dissemination of pollen to conventional fields.

The text is criticised by pro-GMOs who say it does not go far enough and by the antis, including deputies of the ruling majority, who say changes made in exchanges between the parliament and the upper house make it too lax.

LEGAL CONTAMINATION

Approved amendments include a rate of GM dissemination to conventional crops of up to 0.9 percent, a level fiercely contested by ecologists seeking to protect France's biodiversity and organic crops from GM contamination. "The problem of this law is that it legalises contamination because anything with a GMO content of less than 0.9 percent can be called GMO-free," Romain Chabrol, a spokesman of the environmental group Greenpeace France, said. The rate in Germany was set at 0.1 percent.

French Environment Minister Jean-Louis Borloo said the new law would be the "most protective in the world". French President Nicolas Sarkozy has repeatedly said he does not want to close the door on the technology or ban research so as to limit the number of biotech companies put off by the destruction of their outdoor experiments by activists.

French cooperative Limagrain, which has a 70 percent stake in the world's fourth-largest seed maker Vilmorin, said this year its research unit Biogemma had moved its tests on GM crops to the United States after repeated attacks on its fields.

Such attacks would be more severely punished under the law. (Editing by Robert Woodward)