Under-21s shouldn't be allowed to buy tobacco, according to the Royal College of Physicians.
Its policy group on smoking says the minimum age should be increased from 18 - to reduce the number of people becoming addicted.
A recent survey showed 71 per cent of the population aged over 15 years are in favour of increasing the legal age to 21.
Professor Des Cox, the chairman of the RCPI Policy Group on Tobacco, says the move could have a major impact.
"The evidence now tells us that by increasing the age of sale for tobcacoo products from 18-21, we have the opportunity to decrease not only young adult smoking but teenage smoking by up to 25%."
