The European Union said Monday it is taking France to court for failing to adequately prevent water pollution by nitrates under a 1991 law.

"France has still not designated a number of zones that are vulnerable to nitrates pollution, and it has yet to adopt measures to effectively combat nitrates pollution in these zones," the European Commission said.

The European Union executive "is therefore taking France to the EU Court of Justice."

Widely used as fertilisers, nitrates in excess amounts cause severe water pollution, the Commission said.

Designated areas should have "closed periods when manure and chemical fertilisers cannot be spread, a capacity for storing manure when it cannot be spread, and limitations on fertiliser application."

The executive said water quality data show that some parts of France not currently designated "are in fact vulnerable to pollution by nitrates."

The action followed a warning letter sent at the end of October last year.

Despite agreeing to amend national legislation, "slow progress and insufficient proposed changes have led the Commission to refer the case."