Swedish researchers, who examined nearly 300 women in Sudan where the practice is widespread, said on Friday women who had undergone circumcision, or female genital mutilation (FGM), were five to six times more likely to be infertile.

"All sorts of female circumcision, not only the severe forms, probably cause an increased risk of infertility. This is a very important argument to be used in areas where this is practised," Dr Lars Almroth, a paediatrician and researcher at the Karolinska Institute in Stockholm, said in an interview. Despite efforts to stop what human rights campaigners have described as an atrocity against womanhood, female circumcision is practised in Africa and is common in some countries in the Middle East. It involves the removal of part or all of the female genitalia.

An estimated 135 million women and girls have been circumcised, according to the human rights group amnesty International.

It is considered part of the culture, a tradition or a rite of passage to adulthood. In some countries it is viewed as a means of reducing a woman's sexual desire and of safeguarding her fertility.

The research, which is published in The Lancet medical journal, is the first clinical study to show it has the opposite effect.