Washington ? A study commissioned by an anti-smoking foundation says tobacco giant Philip Morris’ campaign to discourage teen-agers from smoking is having the opposite effect.

“Philip Morris should pull its ads off the air at once,” American Legacy Foundation President and chief executive officer Cheryl Healton said Wednesday. “It should call an immediate halt to a campaign that not only doesn’t work but actually harms the very kids it purports to help.”

Howard Willard, senior vice president of youth smoking prevention at Philip Morris USA, said the company was “confident that our youth smoking prevention ads clearly convey the message that not smoking is the right decision for kids to make.”

The Legacy Foundation, created in 1998 as part of the $206 billion tobacco industry settlement with states, hired researchers to compare the effects of Legacy’s “truth” ads with those of Philip Morris’ “Think, Don’t Smoke” campaign. The findings, published in the June issue of the American Journal of Public Health, were based on surveys of roughly 9,000 12- to 17-year-olds conducted before and after the “truth” campaign began two years ago. The Philip Morris campaign began in 1998.

Nonsmoking teens exposed to the Legacy ads were more likely to rule out smoking in the future, the Journal article said, but exposure to the Philip Morris ads “was associated with an increase in the odds of youths intending to smoke in the next year.”

Philip Morris ads often feature teens saying why they don’t smoke and show athletes rejecting cigarettes. In one, a girl turns down a cigarette and goes on to get a black belt in karate.

Michael Wood, vice president of Teenage Research Unlimited, said the young people in the Philip Morris ads don’t look believable, while teen viewers could believe that the “edgy, non-mainstream kids” in the Legacy ads might have considered smoking.

Legacy ads hit teen-agers with stark images and cold facts, said Matthew Farrelly, a health economist and the lead author of the article.

He cited a “truth” ad showing teens dragging body bags in front of a cigarette company’s office. The teens are holding posters stating that 1,200 people die each day from tobacco-related diseases.

Willard said Philip Morris’ research shows that highlighting more immediate smoking-related problems, such as lack of endurance, is more effective than emphasizing the long-term consequences. He said Philip Morris conducts extensive research to ensure its ads are effective.

He cited a government study released earlier this month that showed smoking by high school students dropped to its lowest level in a decade. The study found that 28.5 percent of high schoolers surveyed last year reported smoking a cigarette in the previous month down from 36.4 percent five years ago.

“We believe that our advertisements are one of a number of factors that are contributing to that decline,” Willard said.