Electronic cigarettes should be banned from indoor spaces and face curbs on their sale over health fears, the World Health Organisation has said.
Despite releasing vapour instead of smoke the devices, officially known as electronic nicotine delivery systems (ENDS), still carry a risk to those standing around users, a report for the Geneva-based UN organisation said.
A Wirral Euro MP said the move was unwarranted and that "they should treat adults as adults and leave them to make informed choices rather than introducing a ban."
In a report WHO said: "The fact that ENDS exhaled aerosol contains on average lower levels of toxicants than the emissions from combusted tobacco does not mean that these levels are acceptable to involuntarily exposed bystanders.
"In fact, exhaled aerosol is likely to increase above background levels the risk of disease to bystanders, especially in the case of some ENDS that produce toxicant levels in the range of that produced by some cigarettes."
The report, to be discussed at October's WHO Framework Convention on Tobacco Control in Moscow, also recommends preventing manufacturers from marketing e-cigs as "smoking cessation aids" until they provide scientific evidence to back the claim.
The report also says that they should be banned from sale to minors, and that vending machines should be removed "in almost all locations".
Electronic cigarettes are currently regulated as consumer products in the UK but from 2016 any nicotine-containing products (NCPs) which make medicinal claims - such as claiming they are a stop-smoking aid - will be regulated by the Medicines and Healthcare Products Regulatory Agency.
In its report, the WHO said that so far the evidence that e-cigarettes helped people quit smoking was "limited" and "does not allow conclusions to be reached".
Northwest Euro MP Paul Nuttall, the UKIP deputy leader, said: "They want them to be banned both in public spaces and in work places on the basis that exhaled e-cigarette vapour could increase the background air levels of some toxicants and nicotine.
"Yet at the same time they say that there should be no claims that the devices can help people quit smoking until there is evidence to support this.
"They demand evidence for one but are happy to propose restricting people's freedom without proof of the other.
"Their experts say the devices may also pose a threat to adolescents and the foetuses of pregnant women. Again, they seem to be making assumptions yet tobacco is far more dangerous to unborn children.”
He added: "They should treat adults as adults and leave them to make informed choices rather than introducing a ban. Their proposal to prohibit e-cigarettes to children is, however, sensible as it brings it in line with the age for tobacco sales.”
Action on Smoking and Health (ASH) said it could not support any plans to include electronic cigarettes under smokefree legislation.
Hazel Cheeseman, its director of policy and research, said there was "no evidence of any harm to bystanders from use of these devices" and said regulation needed to be proportionate.