Coca-Cola is selling purified tap water in a bottle, it emerged today.

The company confirmed the source for its new Dasani bottled water, which went on sale last month, was the mains supply to its factory in Sidcup, Kent.

It said a "highly sophisticated purification process" meant the product was "as pure as bottled water gets".

The National Consumer Council said the revelation brought to mind an episode of the BBC series Only Fools and Horses, which was set in Peckham, south-east London.

A spokeswoman said: "It sounds like the episode from Only Fools and Horses when they sold tap water from what they called the Peckham Spring."

Sidcup, where Dasani is bottled, is also in south-east London.

Coca-Cola is investing £7 million in the UK launch of Dasani as part of a worldwide expansion of the brand which is already the second-biggest selling bottled water in the US.

Marketing for the product says water goes through a number of stages starting with three separate filters which take out "particles and organic debris" as well as chlorine.

The next stage, called reverse osmosis, is described as a technique perfected by Nasa to purify fluids on spacecraft.

The process uses high pressure to force the water through the fine membrane, removing "bacteria, viruses, salts, minerals, sugars, proteins and toxin particles".

Calcium, magnesium and sodium bicarbonate are then added for taste, according to Coca-Cola.

Barrie Clarke, spokesman for Water UK, which represents suppliers, said that the suggestion behind the process seemed to be that tap water was impure.

"We don’t think there are any impurities in tap water," he said.

"People don’t need to buy this stuff to get excellent quality, healthy water.

"If they like the bottle, the convenience, the style then fine but I don’t think that is the way they are marketing this product.

"Tap water is pure, and that’s the opinion of the Drinking Water Inspectorate which carries out three million checks a year."

Thames Water, which supplies the Sidcup area, said that its tap water passed 99.92 per cent of quality tests. "If the water regulator thought any more treatment was needed they would ask us to do so," said spokesman Chris Shipway.

Judith Snyder, brand PR manager for Dasani, confirmed they used "municipal" supplies.

"The source of the water is irrelevant - it doesn’t affect the end result," she said.

"And 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 today showed consumers in the UK drank more than two billion litres of bottled water for the first time last year - up 18 per cent on 2002 and from 990 million litres in 1998.

The figures, from food and drink consultants Zenith International, found sales were up 16 per cent to almost £1.2 billion.

Gary Roethenbaugh, research and development director at Zenith, told The Grocer magazine: "Last year was a particularly impressive year for bottled water with the hot summer weather."