Health workers might join gay internet chatrooms to promote safe sex messages after government-backed research suggested that half of gay men go online in search of sex.

A two-year study of more than 4,000 gay men also found that those using the internet were more likely to report high-risk behaviour or a sexually-transmitted infection than others. Only a small proportion of gay men used the internet alone to find partners, said Jonathan Elford, of City University, London, who conducted the study.

"Gay internet sites have provided new meeting grounds ... that did not exist in the early 1990s," said Professor Elford who will report the findings tonight.

The research, funded by the Medical Research Council, might help find new ways to encourage safe sex. Gay men were questioned at HIV clinics, gyms and via internet sites. Three-quarters backed some form of online health advice.