A total of 53 experts from 15 countries including the United Kingdom wrote to the World Health Organisation (WHO) to urge it not to "control and suppress" the devices, saying they have the potential to save millions of lives.
The WHO is preparing to publish recommendations about e-cigarettes to governments later this year.
The letter, whose signatories include Professor Linda Bauld, of Stirling University, urged the global health adviser not to impose regulations on the products in the same way it does with conventional cigarettes.
It said: "The potential for tobacco harm reduction products to reduce the burden of smoking-related disease is very large, and these products could be among the most significant health innovations of the 21st Century - perhaps saving millions of lives.
"The urge to control and suppress them as tobacco products should be resisted and instead regulation that is fit for purpose and designed to realise the potential should be championed by WHO."
The authors of the letter -including experts who have advised the National Institute for Health and Care Excellence (Nice) on its guidelines about reducing the harm from tobacco -published the letter after claiming to have seen a leaked document from the WHO which labelled the e-cigarettes as a "threat".
Signatory, Professor Robert West, of University College London, said: "For the WHO to suggest e-cigarettes are as risky as other tobacco products would send an erroneous message to the millions of current e-cigarette users who have used them to quit smoking.
"It would discourage smokers from trying them and we would miss out on a major opportunity to reduce smoke-related deaths."
Research published last week by Professor West claims e-cigarettes can help improve the success rate of people trying to quit smoking by 60 per cent compared to nicotine patches or gum.