MPs are being warned to curb the sale of ‘electronic cigarettes’ following fears they could be much more dangerous than previously thought.

‘E-cigarettes’ are sold as a healthier alternative to real cigarettes as smokers can get their nicotine fix without inhaling tobacco, tar or carbon monoxide.

But trading standards are concerned children could buy the fakes and suffer exposure to damaging levels of nicotine.

The government should ban sales to under-18s and force manufacturers to label them as hazardous, in line with current regulations for real cigarettes, regulators are now advising.

First developed in China, ‘e-cigarettes’ look almost identical to real ones, but are made of stainless steel and run on batteries.

Inside is a cartridge of liquid nicotine, which vaporises when heated so the user inhales droplets of the drug and breathes out a mist rather than smoke.

Initially the metal cigarettes were traded mainly online, but they are now appearing in high-street stores and market stalls, feeding a demand from consumers trying to dodge the smoking ban.

But tests by UK trading standards officers revealed levels of nicotine in some products that were “highly toxic”, the level that would normally need a warning label. The so-called healthier alternative is already banned in Australia.

The World Health Organisation has raised concerns over a lack of research into the effects of the product, and Lacors, the advisory body for local government, has called for sales to be restricted.

There are also fear children could swallow the small steel cartridges, which could lead to suffocation and death.

Jason Cropper, managing director of the Electronic Cigarette Company, has previously said that tests carried out on mice had shown the safety of the products, although no human trials have been done.