Selling cigarettes to anyone under 21 should be banned, experts have warned.
Boris Johnson's new government should up the legal age to buy fags from 18 to 21.
Campaigners say the move would help achieve the government's target of wiping out smoking by 2030.
The All Parliamentary Group on Smoking and Health has suggested raising the age of sale of tobacco to 21, "to discourage uptake by those most at risk".
It's part of an effort to stop younger 'social smokers' becoming addicts in later life.
Deborah Arnott, chief executive of the health charity Action On Smoking And Health (Ash), told The Sun: "Almost no-one starts smoking after the age of 21, and not starting is much easier than quitting.
"Increasing the age of sale to 21 is a key step towards achieving the Government goal of ending smoking by 2030.
"Smoking is a lethal addiction with two thirds of those experimenting with cigarettes going on to become regular smokers, and only one in three successfully quitting in the long-term."
This week a team of scientists in the US shared their findings, adding weight to the argument for increasing the age of sale to 21.
Lead author, Dr Abigail Friedman at the Yale School of Public Health, said: "This research indicates that a 'social multiplier' effect may amplify the impact of tobacco-21 laws.
"While these policies were associated with a 39 per cent drop in the odds of regular smoking overall, the reduction was larger among young people whose friends were likely to smoke before tobacco-21 laws were adopted.
"As peer smoking is a critical predictor of youth smoking, this study suggests that tobacco-21 laws may help reduce smoking among those most susceptible.
"This result supports raising the age of sale to 21 as a means to reduce young adult smoking and improve public health."
As of June , 16 US states have raised the age of sale of tobacco to 21.
Earlier this year, Dr Nicholas Hopkinson, a specialist at Imperial College London and the British Lung Foundation, argued in the British Medical Journal that raising the age of buying cigarettes to 21 would make it "harder for children to obtain cigarettes and would take the legal age beyond school age".
Achieving a smoke-free generation - where smoking rates are below five per cent in all groups in society - is a "key public health goal".
Dr Hopkinson, who is also chair of Ash, said helping existing smokers quit is important.
But "most vital element is to prevent young people from starting in the first place."
Most smokers start as kids, and two thirds of those who try smoking will go on to become regular smokers.
The habit is one of the leading causes of preventable deaths in Britain, drastically increasing a smoker's risk of various cancers and heart disease.
Dr Hopkinson said increasing the legal age to buy cigarettes will help make it harder for kids buying and selling them at school.
"Smoking is a contagious habit, transmitted within peer groups," he said.
"The age increase will protect younger children from exposure to older pupils who smoke."
