Canadians increasingly choose bottled water over tap water. But a new study by the Sierra Legal Defence Fund argues that in some cities, tap water might be safer to drink.

"Particularly if you're in one of Canada's larger cities -- Toronto, Edmonton, Vancouver -- we would say that buying bottled water is probably a waste of your money," the study's author, Randy Christensen, told CTV News.

The report, "Waterproof 2: Canada's Drinking Water Report Card," focuses on flat bottled water, as opposed to carbonated water or mineral water.

A one-litre brand-name bottle of flat water costs about $1.50. That's about 3,000 times more expensive than an equal amount of municipal tap water.

And according to CTV's Todd Battis, some brands of bottled water actually come from tap water. But each year, more Canadians are buying their water at the store.

In 1997, the average Canadian drank 21 litres of water throughout the year. By 2003, that number had more than doubled to 47 litres per person.

The report attributes the popularity of bottled water to the notion that it's safer than other sources -- a notion that's largely misguided, according to Christensen.

"We found that Health Canada is effectively letting the industry regulate itself," he said.

A major criticism is that companies don't have to release their water test results to the public, unlike Canada's municipalities.

The report also warns about possible health concerns over storing bottled water. The bottles are commonly made of plastic containing the chemical bisphenol A, which scientists say can migrate into the water.

However, research is divided on whether such small exposure to bisphenol A is harmful to humans.

Health Canada is currently reviewing the laws governing the production of bottled water, and said a proposal updating monitoring and testing guidelines will soon be made available.

Meanwhile, municipal water engineers argue companies producing bottled water should be held to the same tough regulations as Canada's cities.

"We monitor the water on a very high frequency basis, to make sure that water is preserved as it goes through the system to the customer's cup," said Bob Jones, a Vancouver water engineer.

According to the Sierra Legal Defence Fund, the Greater Toronto Area also has very high standards. The city conducts about 70,000 bacteriological tests each year on its water supply, for more than 300 chemical contaminants.

Under Ontario's legislation, tests are only required for 78 chemical contaminants.

According to CTV's Todd Battis, some religious leaders are also endorsing tap water.

"It's not just environmentalists complaining. Some church leaders want their faithful to shun bottled water, saying charging money for water is immoral and that it's a sacred gift of nature," Battis reported.

With a report by CTV's Todd Battis in Vancouver