The Conseil Constitutionnel struck down the tax on Tuesday as the exemptions "create a breach of the principle of (tax) equality."

It estimated that 93 percent of industrial emissions outside of fuel use, including the emissions of more than 1,000 of the country's most polluting industrial sites, would be exempt from the tax of 17 euros per tonne of emitted carbon dioxide.

The ruling is a severe blow for President Nicolas Sarkozy as the measure was one of his flagship initiatives to cut emissions of greenhouse gasses that fuel climate change.

It also leaves the government scrambling to plug a hole of 4.1 billion euros (5.9 billion dollars) in the 2010 budget.

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