Light smoking still a cancer risk
Smokers who cut down on the number of cigarettes they smoke or switch to low-tar brands have been urged to kick the habit completely.
Experts have warned that people who reduce their cigarette consumption or opt for lighter alternatives are still at risk of cancer.
They suggested that people who think they are reducing the health risks by cutting down are kidding themselves.
They said in many cases such people simply smoked more intensively, eradicating any potential health benefits.
Professor Martin Jarvis, from the health behaviour unit at University College London, said smokers should try to quit.
"As a first step towards quitting smoking altogether, cutting down can be helpful for some people, but it should not stop there.
"Cutting down can easily be a fool's paradise because, without realising it, people smoke their remaining cigarettes more intensively, and can end up getting just as much exposure to tar and other harmful smoke components as before they reduced their cigarette consumption."
Jean King, director of tobacco control at Cancer Research UK, said some people did not realise that they were still increasing the chances of developing cancer.
"We think there is a danger that people are becoming confused about the health issues surrounding levels of smoking and work must continue to encourage people to quit altogether rather than just to cut down.
"Quitting is not easy as the nicotine delivered in tobacco smoke is a highly addictive substance.
"Furthermore, research shows that people who cut back, or switch to 'low-tar' cigarettes, may often inhale more deeply and can be just as addicted to nicotine as people who smoke more."
Sir Paul Nurse, Cancer Research UK chief executive, added: "Cutting back is only part of the story - giving up altogether should be the ultimate goal."
It is estimated that two out of three smokers in the UK want to give up.
A study published in August suggested that people who smoke just a few cigarettes each day are seriously damaging their health.
The study, by doctors in Denmark, found women who smoke just three cigarettes a day double their chances of having a heart attack and of dying early.
Men run similar risks if they smoke six cigarettes or a cigar each day.