However, many young smokers want to quit.

The research, commissioned by BUPA, found that one in five teenagers are current smokers, and that almost half (49%) had tried smoking.

Nearly half of the teenagers surveyed (43%) had their first cigarette between the ages of 13 and 14.

One-fifth had their first cigarette between the age of 11 and 12.

As many as 8% had their first cigarette before they were ten.

The survey found that two-thirds of teenagers start smoking because their friends have tried it.

A quarter felt they were pressurised into it by their friends.

Only 3% felt celebrities or people smoking on television had any influence.

The overwhelming majority (90%) were with their friends when they had their first cigarette.

Almost a quarter (23%) had their first cigarette at school while a third (30%) had their first cigarette when they were hanging out with friends.

Health concerns

The vast majority (83%) of current smokers want to give up smoking.

Nine out of ten teenagers are concerned that smoking is bad for health but only 24% of current smokers are very concerned, and a quarter are not very or not at all concerned.

However, 87% of current smokers said they would give up if they had children.

Four out of five teenagers dismissed the idea that smoking was cool.

Most knew that it caused lung cancer, and 81% were aware it was hard to give up once hooked.

There was some encouraging news for anti-tobacco campaigners. Six out of ten teenagers said that anti-smoking advertisements on television put them off the habit.

Health risks

Dr Paula Franklin, BUPA assistant medical director, said: "What is most worrying is that so many teenagers are smoking, despite the fact that they are aware that smoking can cause fatal diseases like lung cancer.

"Indeed, a quarter of teenage smokers said they were not concerned about the health risks."

"It is particularly concerning because smoking is highly addictive and it is very hard to stop as shown by the fact that the majority of adult smokers started smoking as teenagers.

"If you can avoid smoking during your teenage years it is less likely that you will take up smoking later in life."

Amanda Sandford, research manager for the anti-smoking charity Action on Smoking and Health (ASH), said: "Despite the disturbingly high number of teenagers who smoke or have tried smoking, it's good to see that the health message is getting through to young people.

"It's also encouraging that such a high proportion want to give up smoking.

"The challenge now is for the health community to recognise this call for help and to find appropriate ways of helping teenagers kick the habit."