The makers of France’s most popular mineral water have angered the Government, the Paris council and Green groups with a campaign implying that the capital’s tap water is undrinkable and polluted.

City officials, who are proud of the quality of their eau du robinet, have hit back, saying that much of Cristaline, the bottled water, comes from the same underground source that supplies an industrial port city.

Behind the feud lie declining sales in a saturated market for mineral water, which the French still drink in greater volumes than the tap version. Cristaline, a low-cost eau minérale, has covered Paris with posters showing an open lavatory with a red cross and the tagline: “I do not drink water that I use.”

Another shows a tap and says: “Nitrates, lead and chlorine . . . I don’t save money on water I drink.” A third says: “Anyone who claims that tap water is always tasty can’t drink it often.”

The adverts, designed to counter a campaign promoting the virtues of municipal water, prompted outrage from Nelly Olin, the Environment Minister, who threatened legal action. “I am angry.

“We do not accept that this company should cast aspersions on tap water. It is dishonest,” she said.

Anne Le Strat, a Green councillor and president of Eau de Paris, the city water authority, was so incensed that she conducted a tasting session at a café to prove that tap water and Cristaline were indistinguishable. This campaign plays on imaginary fears. The consumer is often unaware that bottled water costs between 100 and 600 times more and resembles, sometimes to the point of confusion, tap water,” she said, referring to a disclosure last summer that tap water in the port of St-Nazaire comes from the same water table from which Cristaline draws supplies for its local plant.

Pierre Papillaud, president of Cristaline, said that the adverts were a response to a campaign by the Paris water authority that promotes its eau du robinet as just as tasty as the bottled version. Other cities are going farther than Paris in promoting tap water. The town of Mulhouse puts its water into labelled bottles for receptions.

Sliding sales have forced mineral water makers to seek new customers. While Cristaline was devised as a mass market product, others are going up market to persuade customers that their H20 has gastronomic qualities.

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