The Government is to introduce new legislation to ban under-18s from buying electronic cigarettes.
The Coalition also plans to make it illegal for adults to purchase cigarettes for anyone under 18, under tough new laws aimed at cracking down on teenage smoking.
The announcement comes as e-cigarettes are enjoying a boom in sales, with an estimated 1.3 million people in the UK thought to use them.
The law, which will be introduced this week as an amendment to the Children and Families Bill, will also ban 'proxy purchasing' - knowingly buying tobacco on behalf of someone under 18.
Adults caught breaking the law, which ministers hope will come into force by the autumn, could be given a £50 fixed penalty notice or fined up to £2,500.
Public Health Minister and Conservative MP Jane Ellison said: "Two thirds of smokers say they smoked regularly before they were 18, showing that this is an addiction largely taken up in childhood.
"We must do all we can to help children lead a healthy life. That's why this measure is designed to help protect children from the dangers of being bought cigarettes by irresponsible adults - something that I hope concerned parents and responsible retailers will welcome."?
While many people view the tobacco-free devices as a better alternative to traditional cigarettes, health experts remain deeply concerned about the long-term effects they could have on users' health.
E-cigarettes provide a hit of nicotine - a highly addictive drug - and some fear they reinforce the behaviour of smoking, making it harder to give up in the long term.
England's chief medical officer, Professor Dame Sally Davies, said: "We do not yet know the harm that e-cigarettes can cause to adults let alone to children, but we do know they are not risk free.
"E-cigarettes can produce toxic chemicals and the amount of nicotine and other chemical constituents and contaminants, including vaporised flavourings, varies between products meaning they could be extremely damaging to young people's health."
Currently there is no restriction on people under the age of 18 buying e-cigarettes, and they are hugely popular among teenagers in Briton.
But it is feared that children are turning to the smokeless devices - designed to help users quit - before moving on to traditional cigarettes.
Many secondary schools across the UK have resorted to banning e-cigarettes over fears they are encouraging pupils to take up smoking.
Smoking rates have fallen to their lowest ever, in the wake of the ban on smoking in public and a series of shocking public health campaigns highlighting the dangers of cigarettes.
But more than 1,000 people end up in hospital every day as a result of smoking, and experts have warned that the growth in e-cigarettes could reverse some of the good work that has been done in tackling the dangerous habit.
The latest move comes as Department of Health figures reveal that 41% of 15-year-olds who smoke say they usually buy their cigarettes from other people rather than buying them from a shop.
And 95% of 11- to 15-year-olds who smoke have managed to get someone else to buy cigarettes for them in a shop at least once in the past year.
The proxy purchase of alcohol is already illegal, and retailers have been calling for the creation of a proxy purchasing offence for tobacco for many years.
Smoking is one of the biggest causes of death and illness in the UK. Every year around 100,000 people die from smoking, and it is linked to a string of other potentially fatal illnesses including heart disease and strokes.
Deborah Arnott, chief executive of health charity Action on Smoking and Health (ASH) said: "ASH supports the government decision to make it illegal to sell e-cigarettes to under-18s.
"Although our research shows the only children using e-cigarettes are already smokers, and even then the numbers are small, this is a rapidly growing market and these products are being heavily promoted."
She said of proxy purchasing of tobacco: "We know that buying cigarettes from adults is a major source of supply for under-age smokers, so in principle making buying cigarettes for children illegal is a good idea. We'd also like to see a retail licensing system put in place so that cigarettes could only legally be sold in shops not in car boot sales and markets."