Some gay men who are HIV positive still have unprotected sex
A third of gay men who know they are HIV positive are still having unprotected sex, a study suggests.
The Medical Research Council, which questioned 3,500 gay men, also found 40% of the 300 who tested positive for HIV did not know they were infected.
Dr Lisa Williamson said more sexual risks were taken by men who had been infected with HIV for a long time.
About 2,700 gay men in the UK were diagnosed with HIV in 2006 - double the number a decade earlier.
According to the survey, those who knew they were HIV positive were statistically more likely to have unprotected sex than those who did not.
The researchers are calling for a more targeted approach to prevention - promoting condom use even among men who are regularly tested, and urging those who report high risk behaviour to be tested more than once a year.
Will Nutland from Terrence Higgins Trust on action needed
Will Nutland, from the HIV charity the Terence Higgins Trust, said a recent survey showed a third of gay men had been tested for HIV last year.
He said: "What we don't necessarily want to see is an across the board increase in testing. We want to see gay men who are taking the greatest number of risks testing more often.
"Of course, on the face of it, it seems perfectly simple, but what we do know is that one-third of young gay men leave school without adequate safe sex information.
"We're not equipping those people for their future sex lives and we're not investing the way we that should be in HIV prevention campaigns across the whole of the UK in the communities who are most at risk."
New HIV diagnoses among gay men in the UK are higher than they have ever been.
The 2,700 gay men were diagnosed in the UK in 2006 represent about a third of all new cases that year.
The Terence Higgins Trust says funding for prevention work among gay men is under threat and that there is not enough discussion of the issue within the gay community.
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