NEW YORK — Just say H-2-No.

That's what an increasing number of public officials, environmental advocates and restaurateurs are urging people to do when they're tempted to reach for bottled water.

Rather than spend money on costly plastic containers of water, consumers should boot the bottle and turn on their taps, according to such officials as San Francisco Mayor Gavin Newsom, Salt Lake City Mayor Ross "Rocky" Anderson and Minneapolis Mayor R.T. Rybak.

Those three sponsored a resolution at last month's meeting of the U.S. Conference of Mayors calling for a study to examine the environmental impact that millions of empty plastic water bottles have on municipal garbage operations.

Newsom and Los Angeles Mayor Antonio Villaraigosa have issued executive orders prohibiting the use of city money to buy bottled water, and the Ann Arbor City Council in Michigan last month approved a measure calling for city events to be bottled-water-free.

"For a long time, I've viewed [bottled water] as a huge marketing scam," Anderson said recently, explaining why he has called for Salt Lake City employees to drink tap water and use refillable water bottles.

Municipal water supplies are just as good as bottled water and are monitored far more closely, city officials across the country say. And a gallon of tap water typically costs less than a penny, up to 10,000 times less than an equivalent gallon of bottled water, according to the mayors' resolution.

The bottled-water business calls the attacks unfair. The head of the industry's leading trade group says bottled water's competition is not the kitchen faucet but the soft drinks, sports drinks, iced teas and other beverages that fill grocery shelves.

"I think it's unfortunate there is now this tap-water-versus-bottled-water controversy," said Joseph Doss, president of the International Bottled Water Association, which represents 450 bottlers, distributors and suppliers. "We don't see it that way. I don't think consumers are replacing tap water with bottled water. We make a food product. We see other food products as our competitors."

Only soft drinks outsell bottled water, and their market share has been declining.

"[Bottled water] tends to appeal to younger consumers," said Gary Hemphill, managing director of Beverage Marketing, a consulting firm. "A lot of it has to do with active lifestyles; you're mobile and out and about. The portability is important."

While the bottled-water industry said its growth has not come at the expense of tap water, the amount of tap water Americans drink has been falling.

New York City Health Commissioner Thomas Frieden thinks a generation of younger Americans has grown up thinking tap water isn't safe. That was one reason he teamed with the city's environmental-protection department to produce a $700,000 marketing campaign to urge New Yorkers to drink the city's tap water, often cited as one of the purest water supplies in the country.

For environmental groups such as the Natural Resources Defense Council, the case against bottled water is as clear as a mountain stream.

Manufacturing, transporting and disposing of plastic bottles consumes oil, contributing to global warming and filling landfills. The council estimated that shipping the 43 million gallons of bottled water imported annually from the European Union creates about the same carbon-dioxide emissions as 660 cars running for a year.

"When you factor in that water is something that is free and available to you, and then the oil and plastic that are consumed, and the transportation halfway around the world in some cases, bottled water becomes a product whose value isn't clear," council spokeswoman Jennifer Powers said.