Male pheromones secreted in underarm sweat can make men more sexually attractive to women, according to research.

The study, to be presented to the British Psychological Society's annual conference in Winchester today, found that women who are secretly exposed to male pheromones tended to rate men as being more attractive than they were rated by women who were not exposed to the pheromones.

The team, led by biological psychologist Nick Neave from the University of Northumbria, studied the effects of male sweat hormones on 32 female students. The women were tested both during menstruation and at mid-cycle, and 16 were taking the contraceptive pill.

The female students were asked to rate the attractiveness of various men, using written descriptions, drawn body shapes and photographs, while sitting in laboratory cubicles.

Half of the women were secretly exposed to the male pheromones, which were on cotton wool pads, which had been placed under the arms of healthy young men overnight.

The women who had been exposed to the pheromones found the men more attractive than their counterparts. But the biggest and clearest effect was seen when the women were shown photographs of men.

Those exposed to the pheromones gave an almost two-fold increase in attractiveness rating. This affect was particularly strong in women who did not take the pill but who were at mid-point in their menstrual cycle.

But perhaps the most surprising result found by Dr Neave and his colleagues was that the men who were of average or below average attractiveness benefited most from the use of the pheromones. Dr Neave said: "We used four pictures of men, three of which were of above average attractiveness and one who was below average.

"When women were exposed to the pheromones the above average men were rated slightly higher but the below average man suddenly shot up in the ratings."

Although the research confirmed that male pheromones can significantly affect women's sexual attraction to men, men with average looks may not necessarily benefit from exposing women to their sweaty armpits.

Dr Neave said: "My advice to less attractive males is that if a man sweats and comes into contact with girls who are mid-cycle and not taking the pill, he may see a small positive effect.

"But if he stops washing and using deodorants he will probably start smelling and lose far more friends than he would gain."