Smoking a pack of cigarettes per day can increase the risk of impotence by up to 40 per cent, it has been claimed.

Researchers surveying men in Australia concluded that erectile problems increase in direct proportion to the amount of cigarettes smoked.

Those smoking less than 20 cigarettes were still 24 per cent more likely than non-smokers to join the ten per cent of men who suffer from erectile dysfunction .

"The good news is that quitting smoking greatly reduces the risk of circulatory problems such as impotence," said Deborah Arnott, director of the Action on Smoking and Health (Ash) charity.

"Young men who want to avoid the embarrassment and distress of impotence can help themselves by quitting smoking before such problems arise."

Australia's Study of Health and Relationships also found that cardiovascular disease and old age increased the risk of impotence, but, as Chris Millett from Imperial College London said, such causes "can feel distant".

Mr Millett hopes to provide a wake-up call to the third of men aged 20-24 who smoke in the UK.

"By highlighting this link between smoking and erectile problems we may be able to motivate these men to quit," he said.

Translating the 9.1 per cent impotence ration to the UK population suggests that over 700,000 British men aged between 30 and 50 may suffer some form of impotency.

The Department of Health recently launched a high profile publicity campaign with posters aimed at highlighting the effect smoking has on sexual performance.