Odours given off by breastfeeding women and newborn babies boost the sexual desires of other women, a team of fertility specialists claimed yesterday.

The findings suggest that the odours contain a substance which acts as an aphrodisiac, adding weight to the controversial theory that human pheromones exist and can subtly affect our behaviour.

Scientists behind the discovery said it may be possible to identify the chemical responsible for the effect, and use it to develop a treatment for women who wish to increase their desire for sex.

The survey revealed that those who sniffed pads worn by breastfeeding women reported a 24% increase in sexual desire if they had a partner, and a 17% increase if they were single.

Women who were given fresh pads to sniff showed no significant change in their sexual desires.

Speaking at the annual meeting of the American Society for Reproductive Medicine, Martha McClintock, a psychologist at the University of Chicago, said: "We knew there are other species in which the females use social signals from other females to help time when they become pregnant and have offspring at optimal times, and so we wanted to find out if that was the case in humans."

Researchers speculate that an explanation may lie in the evolution of social groups, when it made sense for groups of women to have newborns at a similar time.