A reluctance to engage with the "promiscuous 10%" in society, because of the protests of a minority who oppose education and discussion about sex, is at the heart of the sexual health crisis, public health experts claim today.

Television, films and magazines foster sexuality and use it to sell products. Yet, say the experts, rarely is a woman or man seen with a condom.

Although chlamydia has taken off and syphilis has returned, the health issues associated with having more than one partner are not part of the script. Behind this conspiracy of silence about the perils of sex is a fear of enraging people who do not want open discussion, particularly in schools, according to Mark Bellis, the director of the Centre for Public Health in Liverpool, and his colleagues.

The result is the neglect of those who most need education - "the promiscuous 10%". In their article in the Journal of Epidemiology and Community Health, they define this significant group as those "who have multiple sexual partners, may have started sex early in life". They say that by the age of 14 one in 10 young people have started having sex, and that those who start young are less likely to use condoms, are more likely to become pregnant earlier and have more sexual partners.

"Changing their behaviour is central to improving sexual health," say the authors, but sex education in schools is, in effect, outside the curriculum, allowing schools to do as much or as little as they choose. There is not much more on offer to adults. Around one in 10 women and one in eight men have had at least two partners at the same time in the past year.

Such behaviour is regularly depicted on TV, but without any reference to sexual health. Sexual innuendo goes unchallenged, yet when Durex ran billboard adverts featuring condoms spelling out "Roger More" they were banned "after a few complaints".

The result of this failure to address the most promiscuous is that 10% of sexually active adults have suffered from a sexually transmitted infection and 13% of the population have visited a genito-urinary medicine clinic. The clinics are now often the first place where the sexually active get relevant health information, the authors say.

Professor Bellis and his colleagues call for more relevant sex education in schools, and for more realistic portrayals of condom use and safer sex.

They add: "Perhaps even the occasional advert could suggest that condoms, not just aftershave, may help improve your sex life."