New national statistics indicate that the proportion of gay men having sex without a condom has nearly doubled in the past four years, not only among established couples but also between casual partners.

The 2000 Male Out postal survey, completed last year by 1832 men, found that 46 per cent had had unprotected sex with a regular partner in the previous six months, up from 25 per cent in 1996. Those who had had unprotected sex with a casual partner rose from 16 to 26 per cent.

The research, presented yesterday by the National Centre in HIV Social Research at the University of NSW, found that well-educated, professional men in early middle age - those who experienced the AIDS epidemic of the 1980s - are most likely not to use a condom.

One of the report's authors, Dr Paul van de Ven, said it was "important to recognise that most gay men do not engage in any sexual risk behavior". There was evidence that a large proportion of the unprotected sex was "in the context of negotiated safety," he said.

This might be an agreement not to use a condom between partners who were both HIV-positive, or who were both HIV-negative, and who came to "some arrangement" about sex outside their relationship.

Men were also engaging in sex practices that had a lower risk of HIV transmission, such as withdrawal before ejaculation.

The survey results also show that homosexually active men are having HIV tests less frequently than in the past, with 40per cent of gay men under 25 either never having had an HIV test or not knowing their HIV status.

"Reliable knowledge of HIV status is a cornerstone of Australia's HIV prevention, care and support effort," Dr Van de Ven said. "The challenge is to find ways to encourage all sexually active gay men to test for HIV and to maintain accurate knowledge of their status."

The president of the National Association of People Living with HIV/AIDS, Peter Canavan, said the report highlighted the need for education on the vexed area of disclosure. He said most participants revealed that they expected HIV-positive men to disclose their status before having sex and that many would avoid sex with HIV-positive men.

"In such an environment, it would appear that there is very little motivation for HIV-positive men to disclose their status at all," he said.