E-cigarettes have the potential to save "hundreds of millions of lives" by cutting smoking rates, a group of scientists have claimed in a letter to the World Health Organisation.
The experts want to make sure e-cigarettes are not classified in the same way as tobacco products such as cigarettes.
Such a move could lead to restrictive measures including higher taxes, bans on e-cigarette advertising and restrictions on their use in public places.
Their letter reads: "These products could be among the most significant health innovations of the 21st century - perhaps saving hundreds of millions of lives. The urge to control and suppress them as tobacco products should be resisted."