A letter signed by more than 50 researchers and specialists, including health expert Professor Robert West, from University College London, said e-cigarettes have the potential to save millions of lives.
It urged the World Health Organisation not to impose regulations on the devices in the same way it does with conventional cigarettes.
The global health advisor is preparing to publish recommendations about e-cigarettes to governments later this year.
The letter said: “These products could be among the most significant health innovations of the 21st Century - perhaps saving hundreds of millions of lives.
“If regulators treat low-risk nicotine products as traditional tobacco products... they are improperly defining them as part of the problem.
“Regulators should avoid support for measures that could have the perverse effect of prolonging cigarette consumption.
The signatories, which also include experts who have advised the National Institute for Health and Care Excellence on its guidelines about reducing the harm from tobacco, published the letter after claiming to have seen a leaked document from the W.H.O. which labelled the e-cigarettes as a “threat”.
A World Health Organisation said: “WHO is currently working on recommendations for governments on the regulation and marketing of e-cigarettes and similar devices.
“This is part of a paper that will be submitted to the parties of the WHO Framework Convention on Tobacco Control later this year.
“We are also working with national regulatory bodies to look at regulatory options, as well as toxicology experts, to understand more about the possible impact of e-cigarettes and similar devices on health.”
Research published last week by Mr West found e-cigarettes can help improve the success rate of people trying to quit smoking by 60% compared to nicotine patches or gum.
But critics say that not enough is known about the long-term effects of the devices, which deliver nicotine in a vapour.