It used to be called the unkindest cut. But now the head of the one of the world's largest Aids charities believes we are on the brink of a revolution in attitudes to circumcision.

Richard Feachem, executive director of the Global Fund to Fight Aids, Tuberculosis and Malaria, said research revealing the protective effect of circumcision against HIV was set to change parental expectations and medical practice across the world. Instead of viewing the operation as an assault on the male sex, it was increasingly being seen as a lifesaving procedure which every parent would want for their sons.

Removing the foreskin is thought to harden the glans (head) of the penis, making it less permeable to viruses. Research conducted in 2005 showed the transmission of HIV from women to men during sex was reduced by 60 per cent if the men were circumcised.

A study published last month calculated that if all men in sub-Saharan Africa were circumcised, it would prevent almost six million new cases of HIV infection and save three million lives over the next 20 years.

Dr Feachem said the finding was one of the most significant in the battle against Aids and offered real hope of slowing the spread of the virus. The issue is to be debated at the World Aids Congress, which opens in Toronto next week.

Dr Feachem said: "We know the factors that cause HIV to spread rapidly in a country - the number of concurrent sexual partners, the use of condoms, the presence of other sexually transmitted diseases and male circumcision. Other things being equal, in a circumcised population you have a low and slowly developing epidemic and in an uncircumcised population you have a high and fast developing epidemic."

He added: "Circumcision is growing strongly in popularity in South Africa and in North America. We see males seeking circumcision very commonly in South Africa. The news of its protective effect caused a substantial increase in demand for adult male circumcision.

"Circumcision fell out of favour in North America and the UK as an unnecessary operation. Following this research, I think it extremely probable that parental demand for infant male circumcision will grow as a consequence."

More than one in three boys were estimated to be circumcised in the 1930s, but it fell out of favour from the 1940s onwards. By 1998, it was estimated that 12,000 circumcisions were being performed each year in Britain, suggesting fewer than one in 25 boys was having the surgery. There are big differences between racial and religious groups.

The rate of HIV infection in west Africa is less than 10 per cent, compared with more than 20 per cent in South Africa, which has mystified researchers.

Catherine Hankins, chief scientific adviser to UNAids, and a co-author of the study of the impact of circumcision on Aids in sub-Saharan Africa, published in the online journal PloS Medicine, said: "In west and central Africa there are high circumcision rates and lower HIV rates. Southern and eastern Africa have lower circumcision rates and higher HIV rates."

Deborah Jack, chief executive of the UK-based National Aids Trust, said the research findings were encouraging.

"It is clear the promotion of voluntary circumcision can play an important role in reducing the risk of HIV transmission," she said. But she warned: "People who are circumcised can still be infected with HIV and any awareness campaign would have to be extremely careful not to suggest that it protects against HIV or is an alternative to using condoms."