Men who smoke a pack or more of cigarettes daily are 40 per cent more likely to be impotent than non-smokers, an Australian study has found.

Researchers from Sydney's South West Area Health Service questioned more than 8,000 men aged between 16 and 59 who took part in the Australian Study of Health and Relationships.

They found that almost one in 10 had suffered erectile problems lasting a month or more during the preceding year.

More than a quarter of the respondents were smokers, one in five of whom smoked 20 or fewer cigarettes a day, and one in 16 smoking more than 20 a day.

According to the researchers, the results pointed to a significant association between smoking and erectile problems.

The link became stronger with increasing numbers of cigarettes smoked.

When compared with non-smokers, those who smoked 20 or fewer cigarettes a day were 24 per cent more likely to report difficulties maintaining an erection.

But those smoking more than a pack a day were 39 per cent more likely to report erectile difficulties.

The study is published in the journal Tobacco Control.