Researchers found that a third of the girls they asked gave weight gain as a reason not to give up smoking and a quarter said it made them less hungry.

The study, published in the Postgraduate Medical Journal, assessed 3,000 schoolgirls in London and Ottawa between the ages of 10 and 17.

Professor Arthur Crisp: Girls wish to be thin

Its principal author Professor Arthur Crisp said the anxieties of young girls were clear.

"We found a very strong association between concerns about weight and wishes to be thin.

"And to a certain extent, the concerns about weight seemed to explain the smoking. Although all girls of all kinds of weight and shape smoke, it tends to be those who are slightly overweight who smoke the most."

The findings showed that:

• about 20% of all the girls smoked.
• the habit was strongest among 15 and 16-year-olds, a quarter of whom were smokers in both London and Ottawa.
• those who smoked were 30% more likely to be overweight and prone to eat too much than those who did not.
• girls were up to three times more likely to take up smoking after starting their periods.
• those who drank alcohol were seven times more likely to be smokers.

Smokers told the researchers they had lost 7kg (more than 14lbs) or more since puberty, which they associated with smoking.

These girls were also the ones most likely to resort to vomiting to control their weight.

Teenage campaigns

Teenage smokers - and young girls in particular - are a key target for health promotion campaigns. These have focussed on combating the image of smoking as something that is trendy.

The HEA has tried to shock teenagers into kicking the habit

Only last month, the Health Education Authority launched a series of shocking posters that showed the damage smoking can do to the body.

However, this survey suggests young girls may ignore this type of campaign because their motivation for continuing with the habit has little to do with being fashionable.

Professor Gordon McVeigh from the Cancer Research Campaign believes a new approach is required.

"We must focus on this link that girls have in their minds between smoking and keeping their weight down.

"We must devise a new strategy to disconnect the two in their heads. We must emphasise that the best way to control weight is with healthy diet and no way should they be smoking.

Youth marketing

Previous research by Professor Crisp has shown a strong link between girls who smoke and incidence of the eating disorders bulimia, binge-eating and anorexia.

The anti-smoking group Ash (Action on Smoking and Health) called on the tobacco industry to halt youth orientated marketing immediately.

Ash director Clive Bates said: "For some teenage girls smoking has more in common with desperate conditions such as anorexia and bulimia than it does with girl power.