Scotland's high-profile smoking ban may ultimately have no effect on the number of people quitting, a leading health official has admitted.

Dr Laurence Gruer, director of public health for NHS Scotland, told MSPs on Holyrood's health committee that the total of smokers asking the NHS for help with giving up had slumped since last year's ban on lighting up in public places.

After an early surge of interest in smoking cessation services just before the ban on March 26, applications are now back to previous levels.

Dr Gruer's comments yesterday will make awkward reading for Health Minister Andy Kerr, who has said he hoped the ban would lead to the "denormalisation" of smoking, and an increase in the number of people giving up the habit.

Dr Gruer said: "We did notice a sharp increase in uptake in nicotine replacement therapy before the ban, which has fallen back to levels where they were before. There may not be a sustained effect from the ban on smoking cessation."

Dr Gruer also said there was disappointment at the numbers of young people and men asking for cessation services.

"Teenagers have great difficulty giving up cigarettes. Many are not interested in coming off because they don't see it as a major issue for them. I don't feel we have cracked what is a serious issue.

"The evidence suggests that addiction can develop within a few weeks, certainly a few months of people starting."

Mr Kerr later told the committee he believed the media, actors and the fashion industry were partly to blame for around a quarter of 15-year-old girls smoking, singling out supermodel Kate Moss for setting a bad example.

He said paparazzi shots of the model with a cigarette in hand encouraged others to start, with many young women using smoking as an appetite suppressant.

He said: "I think the media icons - Kate Moss and others - some have a positive influence on our young people and some can have a negative.

"I do believe, and I don't want to sound like an old fuddy-duddy, there are a lot of messages taken from the media and iconic figures are there to set examples and sometimes those examples are not appropriate ones."

Later, the minister appealed to Ms Moss not to be "so blase" about smoking in public, adding: "If she comes to Scotland she will get good smoking cessation advice."

Roseanna Cunningham, the SNP convener of the committee, said: "It's Kate Moss with the fag in her hand at rock festivals."

The minister said the executive intended to lay legislation raising the legal age for buying tobacco from 16 to 18 before the election recess, although it would be autumn 2008 before it could take effect.

Overall, Mr Kerr said the smoking ban had been a huge success, and no one he had met would wish to revert to the status quo. "I am clear when the history of the Scottish Parliament is written the passage of this legislation will quite rightly be seen as a defining moment in devolution."

MSPs also heard a raft of studies were under way to gauge the effects of the ban. One will involve 5000 P7 children to see if the end of smoking in public places has led to more smoking in the home, as critics of the ban predicted.

Mr Kerr said he would be "alarmed" if that was the case, and promised to take action to address any problem.

MSPs heard a recent study of pubs found there had been an 86% fall in pollution since the ban.