The experts of the Swiss Federal Institute of Aquatic Science and Technology (Eawag) found 6 nanogrammes of the banned pesticide per litre of Evian water.

The concentration is well below the legal limits and is not harmful to health but the finding is seen as significant.

Evian water, which springs directly from the heart of the Alps, is considered so pure that scientists use it to calibrate their measuring instruments.

''The fact that even the Evian springs in the French Alps, which are hardly affected by humans, contain pesticide residues is alarming and shows the far too careless handling of these substances,'' Roman Wiget, president of the the international drinking water association AWBR told the German-language Swiss weekly.

Evian mineral water is owned by the French multinational corporation Danone. The water originates in several sources near Évian-les-Bains, on the southern shore of Lake Leman.