Under-18s are set to be banned from buying electronic cigarettes in England, the Government has announced.
Currently there is no restriction on people under the age of 18 buying e-cigarettes, and there is a fear that they are being used by teenagers - an age group with which the devices are hugely popular - before moving on to traditional cigarettes.
Many secondary schools across the UK have already banned e-cigarettes over fears they are encouraging pupils to take up smoking.
E-cigarette sales have boomed over the last year, with an estimated 1.3 million people in the UK now thought to use them.
The tobacco free devices were designed as a healthier alternative to traditional smoking, or as an aid to quitting, but experts remain deeply concerned about the long-term effects they could have on users' health, with very little research having been carried out.
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.”
The law, which will be introduced this week as an amendment to the Children and Families Bill, will also ban people from knowingly buying tobacco on behalf of someone under-18.
Adults who are caught flouting 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.”
The latest move comes as Department of Health figures show that 41 per cent of 15-year-olds who smoke say they usually buy their cigarettes from other people, rather than a shop.
95 per cent of 11- to 15-year-olds who smoke meanwhile say they have been able to get someone to buy cigarettes for them at least once in the past year.
Smoking is one of the biggest causes of death and illness in the UK - every year around 100,000 people die as a result of the habit.
Additional reporting from PA