Lonely and vulnerable gay men are visiting seedy backrooms to deliberately infect themselves with HIV, a new study claims.

Researcher Dr Melanie Parker said members of the gay community were increasingly worried about extreme factions - dubbed bug-chasers - who craved membership to what they see is an exclusive "HIV club".

She said these men felt "marginal, lonely and desperate to belong" and were drawn to sordid "backrooms" at gay clubs, bars and saunas to have unprotected sex with sufferers.

HIV support workers in Sussex have expressed their dismay at the fact some gay men felt this way but stressed it was only a very small fraction of the gay community.

Dr Parker, from Brunel University in west London, said: "HIV is almost certainly being transmitted with a deliberate recklessness in backrooms of clubs, pubs and saunas.

"These men begin to get a sense that those who have a diagnosis of HIV are a distinct group. They have a lot of benefits, like healthcare and help in housing.

"It's possible these men look on with envy and see that some of their problems could be solved.

"Gay men are all talking about it and are very concerned about it and want action.

"The problem is, policy-makers and researchers don't want to enter into that field. They want to brush it under the carpet."

Paul Martin, sexual health manager for the Brighton and Hove Primary Care Trust, said: "We have heard of individual 'bug-chasers' who have the idea of becoming HIV positive, thinking it will bring benefits like getting people to take notice of them and care about them.

"But it is very uncommon - less than one per cent, according to surveys.

"If a person was seeing a counsellor or adviser and raised this type of issue, it would be dealt with but it's not something we're campaigning on on a larger scale."

Jenny Harper, assistant director for residential services at the Sussex Beacon, said staff there concentrated on treating Aids sufferers and did not ask about how it was transmitted.

She said: "I can't comment on whether we've come across people who have deliberately infected themselves. But we would point out that there is no cure for HIV - it's a life-changing and life-threatening illness."

Alan Bond, of White Street, Brighton, a member of Brighton and Hove Lesbian, Gay, Bisexual and Transgendered society (LGBT), said: "This isn't something I've ever heard of.

"These people sound like cases not just for HIV treatment but mental treatment."