A lecturer from the University of the West of England has urged people to stop drinking bottled water.

It comes after a survey by consumer watchdog Which? found half of the population cannot taste the difference between the two.

In fact, almost a fifth of the 3,039 people polled in the blind tasting preferred the flavour of tap water.

Andrew Mathieson, senior lecturer in environmental health at UWE, said bottled water has a damaging impact on the environment as well as leaving a hole in consumers' pockets.

Tap water, at an average of 0.22p a litre, is 141 times cheaper than the best-selling mineral water, Evian, which costs 31p a litre in supermarkets.

Britons spent £1.68 billion on 2.275 billion litres of bottled water in 2006.

But nearly a quarter of those surveyed said they were drinking less bottled water than a year ago.

Mr Mathieson said: “The cost of extracting the water, putting it in a plastic bottle and transporting it thousands of miles leaves a massive carbon footprint.

“I fundamentally recommend people use tap water because by buying bottled water you are paying pounds for a product that costs pennies.

“In the South West, our tap water is as good for you and is similar in quality to mineral water found in the shops.”

Separate research by retail analysts TNS in April found sales of bottled water dropped by nine per cent last year.

Bristol-based supermarket chain Somerfield confirmed its stores had seen a decline in sales of water, in line with the rest of the grocery market.

Which? cited environmental reasons for the drop, saying that for every litre of water purified and bottled, seven were wasted, and that plastic bottles could take up to 450 years to decompose

Richard Hall, chairman of Zenith International, which owns bottled water brand Highland Spring, dismissed the findings and said bottled water was not bad for the environment.

“Tap water leaks more in half a day than the UK bottled water industry uses in an entire year,” he said.

British Soft Drinks Association spokesman Richard Laming denied bottled water sales were declining, and added: “Bottled water comes from fully sustainable sources and accounts for just 0.03 per cent of the nation's carbon footprint.”