Health experts criticized a recent World Health Organization report on e-cigarettes, calling it misinformed and alarming.

Researchers at the National Addiction Centre at King's College London said that the guidelines issued by WHO will prevent people from using these devices to quit smoking.

The UN health agency had said that e-cigarettes should not be used indoors and that these devices should not be sold to minors.

"We were surprised by the negativity of the commissioned review, and found it misleading and not an accurate reflection of available evidence. E-cigarettes are new and we certainly don't yet have all the answers as to their long-term health impact, but what we do know is that they are much safer than cigarettes, which kill over 6 million people a year worldwide," said Ann McNeill, lead author from the National Addiction Centre at King's College London, according to a news release.

Some health experts believe that e-cigarettes can act as "gateway drugs" to addiction and substance abuse. A recent study had found that exposure to nicotine led to increase in cocaine dependence in mouse models.

E-cigarettes use battery-powered cartridges that produce a nicotine-laced vapour. Their popularity, especially among young adults, has soared in the past two years.

The critique of the WHO report by McNeill and her co-authors has been published in the journal Addiction. The report suggests that e-cigarettes expose bystanders to toxic chemicals and that these devices prevent smoking cessation. According to McNeill and colleagues, there is currently no evidence to back these claims.

"E-cigarette use has been a consumer led revolution, the speed at which these products have developed and evolved shows just how much smokers are ready to adopt harm-reduction products. The use of e-cigarettes could save millions of lives during this century, and have the most important public health impact in the history of tobacco use," said Dr Jacques le Houezec, co-author and consultant in Public Health and Tobacco dependence in France.