Over 50 scientists have sent a letter to WHO urging it not to control e-cigarettes

Over 50 public health specialists have urged the World Health Organisation (WHO) not to "control and suppress" e-cigarettes.

In a letter, signed by the health experts, specialists detail the health benefits of e-cigarettes and that the product could potentially save millions of lives.

The BBC originally obtained the letter, signed by 53 experts, which reads: "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.

"We are deeply concerned that the classification of these products as tobacco will do more harm than good.

"The potential for tobacco harm reduction products to reduce the burden of smoking-related disease is very large."

Critics of the e-cigarettes argue that the long term health implications of the tobacco substitute are not known, and Who want the same sales restrictions as tobacco applied to electronic cigarettes.

A spokesperson from Who told the BBC: "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."

The uptake of e-cigs has soared in the past year. According to figures from Ash, an anti-smoking campaign, the usage of e-cigarettes has tripled in the last two years, from 700,000 to 2.1 million.

One third of e-cig smokers are former smokers, according to Ash. In 2010, only 8.2% of current or ex-smokers had tried electronic cigarettes. By 2014, this figure had risen to 51.7%.