The report, which gathers together various research studies, suggests students are actually more likely to take up smoking after they start their medical training.

New government guidelines on reducing smoking stress the role of health professionals in getting people off the tobacco habit.

But, writing in the journal Thorax, Australian researcher Robyn Richards says health workers should look at themselves before trying to convince others to quit smoking.

He says smoking rates range widely among medical students, with Europeans more likely to smoke than Asians.

In some schools almost half the students smoke.

But in many countries students are less likely to smoke than their teachers.

Between 45% and 69% of final year medical students thought their teachers should kick the habit, but in the UK 71% said it was up to the teacher if they gave up or not.

Professor Richmond disagrees. He says: "Leadership from the medical profession is essential if the world is to reduce preventable diseases caused by smoking."

Early training

Research shows that half of all long-term smokers will die of a tobacco-related disease, including heart disease and various forms of cancer.

While smoking has been decreasing in the West over the last 13 years, there has been a 50% rise in developing countries.

Professor Richmond believes medical students should be taught early on in their training about the dangers of smoking.

The fact that students were more likely to take up smoking in medical school than give it up suggested they were not getting information on the dangers until too late in their course, he said.

However, medical students were slightly less likely to smoke than others of their age group.

Lung disease

Professor Richmond's report gathers together information from 9,000 students from 51 medical schools in 42 countries.

Trainee doctors are more likely to take up smoking than give it up

Many students were ignorant about smoking risks. They knew of the dangers of developing lung cancer, but were not so clued up on the links with other illnesses.

For example, less than half of trainee doctors in Holland knew that smoking increased a person's chance of developing cancer of the bladder.

One study showed that only 11% of medical schools had a specific module on tobacco and 12% did not cover smoking at all.

In Africa and Asia, a quarter of schools did not cover tobacco risks.

"What emerges from the many studies conducted worldwide is the great deal of work that is required to rectify the situation, particularly in developing countries where the full impact of the smoking epidemic is yet to be experienced," writes Professor Richmond.

Teaching aids

He describes a teaching aid called Smokescreen Education Program which was developed at his university in Sydney.

It educates students about the health effects of tobacco use, aims to raise awareness about the opportunities they have to intervene to stop patients smoking and teaches students how to motivate patients to give up.

It uses a mixture of lectures and practical aids, including carbon monoxide monitors and spirometers for measuring lung functioning.

The programme has been tried out in several countries, including China where one university has a policy of asking medical students to sign a pledge not to smoke during their training.

Those who do get one warning and are then expelled. If staff are found smoking, they are fined a quarter of their monthly salary.