"The growing of corn seeds... derived from genetically modified corn strain MON810 is prohibited on (French) territory," read the order signed by agriculture minister Michel Barnier.
Monsanto's 810 maize had been the only GMO, or genetically modified organism, crop grown in France, but the French government last month began moving to ban its further use after a watchdog authority said it had "serious doubts" about the product in a report that has been controversial even among the scientists who put it together.
The agriculture ministry order said the ban would remain in force until a decision was taken whether to renew the authorisation for the strain to be sold on the French market.
Farmers to challenge ban
French corn farmers have already said they planned to challenge the ban in court.
With the law requiring a hearing within three weeks, corn producers could still plant the variety of corn this spring if France's highest administrative court supports their appeal, said Luc Esprit, director of the Association General of Corn Producers.
The association estimates that without a ban some 100 000 hectares of the GMO corn would be planted this year, up from 22 000 hectares in 2007.
It estimates the ban would cause farmers losses of some €10m.
France, last month, invoked a European Union (EU) safeguard procedure to temporarily bar Monsanto's 810 maize.
Not safe
It followed a report by France's Provisional High Authority on GM Organisms that said it had "serious doubts" as to the safety of MON810.
It pointed to what it described as "a certain number of new scientific facts relating to a negative impact on flora and fauna".
Chairperson Jean-Francois Le Grand, who also holds a seat in the Senate, said evidence had emerged that MON810 had an effect on insects, a species of earthworm and micro-organisms.
There was also concern that wind-borne pollen from MON810 could travel much further than previously thought - perhaps as much as hundreds of miles, said Le Grand.
The government action also followed French anti-globalisation activist Jose Bove - who has been convicted of ripping up GMO crops in southern France - launching a hunger strike to press for a year-long ban on genetically modified crops.
- Dow Jones