The first British television advert showing the use of an electronic cigarette is to be aired following the introduction of new rules.

It will not be the first time e-cigarettes have been advertised, but it will be the first time one is being used and its vapour exhaled.

The regulations introduced by the UK Committee of Advertising Practice say adverts must not "be likely to appeal particularly to people under 18, especially by reflecting or being associated with youth culture, encourage non-smokers to use e-cigarettes", or "claim e-cigarettes are safer or healthier than smoking tobacco."

The first ad, which shows a woman using an e-cigarette, will air after the watershed and is scheduled to run for five weeks.

Dave Levin, from VIP, the company behind the advert, said: "This advert will mark the first time in almost fifty years that TV audiences see someone exhale what appears to be cigarette smoke on an advert, however, it is actually vapour from an e-cigarette that they will see."

GP Dr Daisy Bennett warned against dangerous marketing practices.

She said: "There are different flavours coming out with e-cigarettes and flavours such as candy flavours, pop-corn flavours I think are, seem like they are targeting children."

Medical experts are generally agreed that e-cigarettes are too new to judge their health effects. The World Health Organisation (WHO) is calling for new laws to restrict their use indoors.

Pro-smoking campaigners have welcomed the relaxation of advertising rules.

Simon Clark, from the lobby group Forest, said: "The evidence suggests that the only people using e-cigarettes at the moment are current smokers or smokers who wish to cut down or quit," he said.

"For that reason, we should encourage the advertisements to be as attractive to them as possible because if they're not attractive, they're not going to quit."