The French government seems to have concluded that a carbon tax slated to go into effect in July would damage the country’s economic competitiveness:

Jean-Francois Cope, parliamentary leader of the governing UMP party, was quoted as saying the tax “would be Europe-wide or not (exist) at all”.
Prime Minister Francois Fillon told parliament that the government should focus on policies that increased France’s economic competitiveness.
France had been rethinking the tax after a court rejected it last year.
The Constitutional Council said there were too many exemptions for polluters in the tax plan, and that a minority of consumers would bear the burden. . . .
“We have to amplify measures that help reinforce the competitiveness of our economy,” Mr Fillon was quoted as saying by Reuters news agency.
“In that spirit, I would like to indicate that the decisions we are going to take regarding sustainable development have to be better coordinated with all European countries, so as not to widen our gap in competitiveness with our neighbour Germany.”

The EU is still considering a zone-wide minimum tax on carbon.