Men who smoke a pack of cigarettes a day are 40% more likely to be impotent than non-smokers, according to new research.

The researchers suggest the prospect of sexual problems in the future may offer the deterrent needed to encourage young men to quit smoking.

The study, published in the journal Tobacco Control, focused on the responses of more than 8,000 men, aged 16 to 59, who were taking part in the Australian Study of Health and Relationships. Almost one in 10 said they had experienced erectile problems over a period of a month or more during the previous year.

More than a quarter (27.2%) were current smokers, and 6% of those smoked more than 20 cigarettes a day. Statistical analysis showed the more cigarettes the men smoked daily, the more likely they were to suffer impotence. Those who smoked 20 a day or less were 24% more likely to report difficulties, while those who smoked more than 20 a day were 39% more likely to say they had problems.

Christopher Millet, from Imperial College London, and colleagues in Australia say the study also shows that men who are older, have a lower level of educational attainment or take heart medicines have a greater chance of erectile dysfunction. On the other hand, moderate drinking - one to four units of alcohol a day - reduced men's chances of impotence.