But a survey released today by the watchdog magazine Which? reveals half of consumers cannot taste the difference between bottled and tap water. And 18 per cent of

the 3,039 people who took part in a blind-tasting preferred the flavour of tap water.

But there are signs that the cost of bottled water is turning buyers off. Consumers in the UK spent £1.68 billion buying 2.275 billion litres of bottled water in 2006. The best-selling mineral water, Evian, will set you back some 31p a litre, while tap water costs an average of 0.22p a litre – 141 times cheaper.

Nearly a quarter of those surveyed by Which? said they were drinking less bottled water than they did a year ago, while separate research in April, by the retail analyst TNS, found sales were down 9 per cent last year.

Neil Fowler, the editor of Which?, said: "There are plenty of good reasons for choosing tap water. You can save money, it's better for the environment and it can taste just as good – if not better.

"The UK has some of the safest and best-quality drinking water in the world. It's time we started appreciating it."

According to Which?, the bottled-water production process wastes an estimated two gallons of water for every gallon purified to put into a bottle.

Some bottled water came from as far away as New Zealand, and most plastic bottles went to landfill, where they can take up to 450 years to decompose.

The consumer group said it supported the installation of free tap water refilling stations in public spaces.

Professor Leigh Sparks, of the Institute of Retail Studies at Stirling University, said: "We are all more aware of green issues and the whole life cycle of bottled water is up for examination."

Owen Davis, of Friends of the Earth Scotland, said: "This Which? report really puts paid to the last myth about bottled water – that it tastes better."

But Richard Laming, of the British Soft Drinks Association, said: "More than 75 per cent of bottled water drunk in the UK is sourced from UK producers, and the majority of the rest comes from nearby on the Continent.

"Bottled water comes from fully sustainable sources and accounts for just 0.03 per cent of the nation's carbon footprint."

BACKGROUND

BOTTLED water became a political issue earlier this year when Phil Woolas, the UK environment minister, delivered a stinging attack on the industry, claiming it was bordering on "morally unacceptable" that Britons drank millions of litres of bottled water in lieu of perfectly safe tap water. The attack was sustained by Tim Lang, the government's natural resources commissioner, who said the only way to combat increasing sales was to make bottled water as unfashionable as smoking.

Sales briefly dipped, but have since rebounded.