About one percent, or 70 million, of people worldwide belong to what researchers are now calling the 'fourth sexual orientation', a small group of 'asexual' men and women who feel no sexual attraction to other people, (New York) Medical Daily reports citing an expert.

Anthony Bogaert, an associate professor at Brock University in Canada, said that the sexualization of popular culture has turned many people off sex.

In fact, society has bombarded people with so much sex to the extent that millions do not have physical attraction to others at all, Bogaert suggests.

Bogaert's book, Understanding Asexuality, claims that an increasing number of people consider themselves asexual and argues that these people are "an under-studied population" who sometimes feel excluded from our "very sexualized culture".

Researchers believe that a certain number of asexuals may have always existed but are only now "coming out", joining up and establishing a common identity as society becomes more liberal, the Medical Daily reported.

Bogaert defines asexuality as an enduring, complete lack of sexual attraction.

"There are two forms - people who have some level of sex drive, but don't direct this drive toward others, and other people who have no sex drive whatsoever," he said.

In 2004, Bogaert analysed the responses of 18,000 people in Britain to a 1994 survey on sexual attraction.

He found that one percent agreed with the statement "I have never felt sexually attracted to anyone at all", the Medical Daily reported.