Smoking by teenagers fell sharply and steadily between 1997 and 2003, but the latest data from a large federal survey tracking smoking and other risky behaviors among young people found the proportion of teens who smoke leveled off between 2003 and 2007.

"This is the most dramatic indication that the great progress we're making has stalled," said Terry Pechacek of the federal Centers for Disease Control and Prevention in Atlanta, which released the new data last week. "This has very negative long-term implications." Anti-smoking advocates agreed.

"More progress must be made to ensure youngsters at these critical age levels continue to turn away from smoking," Cheryl Healton of the American Legacy Foundation, a Washington-based anti-smoking group, said in a statement.

"The lack of greater progress in recent years is a clear warning to elected officials to resist complacency and redouble efforts to reduce tobacco use. We know how to win the fight against tobacco use, but we will not win it -- and our progress could even reverse -- without the political leadership to implement proven solutions," Matthew L. Myers of the Campaign for Tobacco-Free Kids, a Washington advocacy group, said in a statement.

The data released last week come from the Youth Risk Behavior Survey, a nationally representative survey that the federal government conducts of students in grades 9 through 12 every two years to track a variety of risk behaviors, including drug, alcohol and tobacco use.

The proportion of students who smoke soared from 27.5 percent in 1991 to 36.4 percent in 1997 but then began to fall, hitting 21.9 percent in 2003. The 2005 survey, however, showed the rate had crept up to 23 percent. Because that change was not statistically significant, officials were waiting for the 2007 figures to determine whether the downward trend had actually stalled.

The 2007 figure is slightly lower at 20 percent, but again, the figure is not statistically significant.

"We had a dramatic increase from 1991 to 1997 and then a reversal of that problematic upward trend from 1997 to 2003. In 2005 it was not declining, but we hoped that was a short-term bump," Pechacek said. "We're always cautious about making long-term implications from one data point. We were hoping that we would be back on track this year. But we're not."

While the survey did show continued declines in some groups, most notably African American girls, the overall downward trend stalled.

"There have been fluctuations between subgroups, but the bottom line is we are not on the decline anymore. We are confident that is a scientifically defined fact," Pechacek said.

"One in five kids is still smoking. Another generation is continuing on with a high rate of tobacco use into adulthood where the industry can prey on them and maintain this epidemic into another generation," he said. "This is a major public health concern."

Pechacek blamed the trend in part on cuts on anti-smoking campaigns by states that had been funded by a nationwide 1998 settlement of a class-action lawsuit against the tobacco industry.

"Many large states had very active campaigns that went off the air," he said, citing Massachusetts, Florida and Mississippi as examples of states that had cut their programs.

At the same time, cigarette companies have continued to increase their spending on promotional activities, including heavily advertising brands that teenagers are most likely to smoke, working to feature smoking in movies and videos and offering pricing incentives that offset increases in cigarette prices.

"The tobacco industry never stopped promoting its products," Pechacek said. "They have increased their effort and maintained a very active effort to promote tobacco while prevention efforts have lost funding."

Bill Phelps, a spokesman for Altria Group, the parent company of Philip Morris USA, said his company has a variety of programs aimed at discouraging teen smoking, including punishing stores found selling cigarettes to children.

"We believe kids should not use tobacco," Phelps said. "We have a pretty significant youth smoking prevention program.