The French parliament on Thursday adopted a bill to partially privatize the state-run electricity and gas utilities, a plan that had sparked broad protests from labor unions.
Opponents of the measure to allow for the sale of stakes in Electricite de France and Gaz de France said they would appeal to the Constitutional Council, France's highest administrative body.
Unions fear that changing the status of EDF and GDF would signal the start of full privatization. Many Socialist and Communist deputies voted against the bill.
The center-right government argues the move will allow the companies to seek private investors and raise needed funds to defend themselves in a European energy market being opened up to competition.
Over the last few months, striking power workers intermittently switched off street lights, cut electricity to homes and held massive protest marches against the plan.
Protesters pulled the plug on the French presidential palace, the Eiffel Tower and the homes of politicians -- including the private home of Prime Minister Jean-Pierre Raffarin.