PARIS (Reuters) - France published a decree on Monday to prevent the planting of genetically modified maize as a stopgap measure, while the government works on changes to domestic and European laws to ensure a longer-term ban.

The French government, which maintains that GM crops present environmental risks, has been trying to institute a new ban on GM maize (corn) after a senior court twice struck down similar measures.

But in a surprise move, the French Senate late on Monday rejected a proposed domestic law banning GM maize crops with a majority of voters adopting a motion of inadmissibility claiming the attempt as unconstitutional.

Monday's decree was timed to avert any sowing of GM maize by farmers before a law banning planting of GMOs (genetically modified organisms).

After the rejection at the Senate a new attempt to pass a domestic law banning GMO crops would need to be submitted through the other assembly, where the ruling party has a clear majority.

The government said its decree would come into force following a three-week consultation period that runs to March 9. Annual sowing of maize in France gets under way in the second half of March.

"This will prevent there being a period during which GM maize could be sown," a farm ministry spokesman said.

The current Socialist government, like its conservative predecessor, has opposed the growing of GMO crops in light of public suspicion and widespread protests from environmentalists.

Only one GMO variety is currently authorized for cultivation in the European Union - Monsanto's MON810 insect-resistant maize. A GM potato was cleared by the European Commission, but later blocked by a court.

Longstanding differences between EU countries resurfaced last week when they failed to agree on whether or not to approve another GM maize variety, Pioneer 1507, developed by DuPont and Dow Chemical, leaving the way open to the EU Commission to clear it for cultivation.

France is now trying to win support to overhaul the EU rules.

It was one of 12 countries to sign a letter last week warning the Commission against approving Pioneer 1507. France is also trying to reach a common position with Germany ahead of a joint cabinet meeting in Paris on Wednesday.

"We need to give a legal framework to those countries that do not wish to see GM maize grown," French Agriculture Minister Stephane Le Foll told France Inter radio on Sunday.

(Reporting by Gus Trompiz, Sybille de La Hamaide, Valerie Parent and Emile Picy; editing by Jane Baird and G Crosse)