Smokers who use new electronic cigarettes to circumvent the ban on smoking in public places have been warned that they may be damaging their health.

The battery powered, steel gadgets are designed to look like real cigarettes, with a glowing end and a plume of fragrant smoke, but instead of inhaling tobacco the user breathes in a mist of nicotine that is absorbed in the lungs.

The popularity of so-called e-cigarettes is growing as they are legal to smoke inside bars, and cheaper than cigarettes. A starter kit costs £40, while a refill cartridge of liquid nicotine in different concentrations — roughly the equivalent of a pack of cigarettes — costs from 50 pence to £1.

Companies that sell the product claim that they are "100 times healthier" than real cigarettes, with none of the carcinogens associated with tobacco. But the World Health Organisation today warned smokers to beware of the devices, which it said had not been tested adequately.

“If the marketers of the electronic cigarette want to help smokers quit, then they need to conduct clinical studies and toxicity analyses and operate within the proper regulatory framework,” said Douglas Bettcher, director of WHO’s Tobacco Free Initiative.

“Until they do that, WHO cannot consider the electronic cigarette to be an appropriate nicotine replacement therapy.”

Anti-smoking campaigners agreed with the WHO, saying that smokers should stick to the tried and tested nicotine replacement therapies rather than try an untested device.

“In principle we think it’s a good idea for smokers to switch to safer forms of nicotine, but at the moment we don’t know enough about this product," said Deborah Arnott, director of Action on Smoking and Health (Ash).

“Quality control in China [where they are manufactured] is not the highest, and our advice is it’s best to use nicotine products like gums and patches. The electronic cigarettes fall into a regulatory gap and they haven’t been chemically tested.”

Companies that market the e-cigarettes defended their product. “It’s a healthier way of smoking. You don’t get any of the stuff that’s in regular tobacco," said Jason Cropper, managing director of the Electronic Cigarette Company.

“It’s better if people aren’t using nicotine in any form, but they’re an alternative to using a tobacco-based product and my opinion is they’re massively less harmful.

“I bet my life they’re 100 times healthier than using a tobacco-based cigarette.”

Mr Cropper said that testing had been done on his electronic cigarettes: “Apart from the nicotine, the samples tested appear to be free from other harmful toxins.”

He added: “I believe this product is a life-saver. Ultimately it will become the nicotine replacement therapy of choice.”

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