France’s Constitutional Council struck down a tax on carbon dioxide emissions that was to have gone into effect on January 1, part of President Nicolas Sarkozy’s plans to slash the country’s output of greenhouse gases.
The Constitutional Council is the body that ensures the constitutionality of French legislation.
It says there were too many exemptions in the measure taxing emissions by households and businesses and that the tax burden was not shared fairly.
Mr Sarkozy has argued that a carbon tax is essential in the face of threats to the climate and the need to reduce France’s dependence on oil.
Prime Minister Francois Fillon said in a statement that he would make a new proposal soon to respond to the Council’s concerns.