11:26 31 March 2015
Researchers in northwest England have found that many teenagers, including those who have never smoked, are experimenting with e-cigarettes.
Prof Mark Bellis said: "To many people the numbers we've identified might come as a bit of a shock.
"This is just being drawn into a repertoire - another drug that people can use to experiment with rather than being seen as an alternative to tobacco.
On nicotine, he said e-cigarettes were "providing a concentrated form of a highly addictive substance, with known problems associated with it, and we need to be very cautious about that and how we protect our young people."
Electronic cigarettes mimic the effect of real ones. They also produce vapour that is said to be less harmful than cigarette smoke. However, the vapour usually contain nicotine, which can be extremely addicting.
Based on the analysis by Liverpool John Moores University, 5per cent of teenagers who have never smoked before used e-cigarettes while 50per cent were former smokers.
Katherine Devlin, president of the Electronic Cigarette Industry Trade Association, told the BBC: "Obviously, teenagers accessing vaping products is a serious concern.
"[However] since the survey only records a single access, it doesn't provide any information about whether or not they go on to regular use.
"Other statistical data indicate that this is unlikely. Nevertheless, we hope that the newly introduced mandated age restrictions can reduce this number."