Soft drink giant Coca-Cola has admitted it is selling purified tap water in a bottle.
Tap water is the source for Coca-Cola's Dasani product
It says the source for its new Dasani bottled water is the mains supply at its factory in Kent.
The company says Dasani is "as pure as bottled water gets" due to a "highly sophisticated purification process".
But the UK water industry is worried that the marketing of the product implies tap water is impure, which experts say is not the case.
Coca-Cola is investing £7m in launching Dasani, which has become the second most popular bottled water in the US following its launch there in 1999.
Marketing for the product says it goes through four stages of production before it is bottled, starting with being passed through three separate filters.
Coca-Cola says "reverse osmosis", "a technique perfected by Nasa to purify fluids on spacecraft", is then used to filter the water further before minerals are added to "enhance the pure taste".
Finally, "ozone" is injected to keep the water sterile, the company says.
But water industry representatives say consumers do not need to buy Dasani to get "excellent quality, healthy water".
'Tap water pure'
Barrie Clarke, spokesman for suppliers' representative Water UK, said: "We don't think there are any impurities in tap water.
"If people like the bottle, the convenience, the style, then fine, but I don't
think that is the way they are marketing this product.
Dasani is the second biggest selling bottled water in the US
"Tap water is pure, and that's the opinion of the drinking water inspectorate,
which carries out three million checks a year."
Judith Snyder, brand PR manager for Dasani, confirmed "municipal" water supplies were used but said the source was "irrelevant" because it "doesn't affect the end result".
She said: "We would never say tap water isn't drinkable.
"It's just that Dasani is as pure as water can get - there are different levels of purity."
Research published on Wednesday shows that UK consumers drank more then two billion litres of water in 2003 - up 18% on 2002.