A new HIV campaign has been launched in Brighton and Hove after an anonymous survey of men in the city's gay clubs and bars revealed one in eight have HIV.

Research by the Terrence Higgins Trust also found almost half of gay men had had unprotected sex during the last year and a third of HIV-positive men did not know they were carrying the virus.

Researchers took oral swabs to test for HIV, which can lead to AIDS, and asked the men a series of questions about their sex lives.

The trust has launched the 1 In 8 campaign to encourage the use of condoms and minimise infection rates.

Perry French, regional manager at the Terrence Higgins Trust South, based in Ship Street, Brighton, said the infection rates in Brighton and Hove were about the same as in London and Manchester.

He said: "The campaign is reminding people they need to carry on being responsible.

"We know that there is a very high percentage of condom usage within the gay community.

"People are actually very careful but we need to make sure they aren't becoming complacent.

"AIDS has been around for 20 years so we need to keep looking at new ways of making the point it is still around and giving gay men information about how to minimise the risk of infection."

The charity has provided posters for gay venues along with safer sex packets containing condoms and lubricant, some bearing the 1 In 8 campaign logo.

The total number of people attending NHS services for HIV in Brighton and Hove has been rising by between ten and 15 per cent a year, from 810 in 2003 to 920 in 2005.

This is partly because modern treatments make it possible for HIV positive people to have an almost normal lifespan.

Dr Martin Fisher, a consultant at the Elton John Centre, part of the Royal Sussex County Hospital, said: "There are a lot of people who don't believe they have been put at risk.

"Other people put their heads in the sand and don't go for sexual health screenings."

He said early detection made the condition easier to treat effectively and reduced the risk of the virus being passed to sexual partners.

Anna Bamford, HIV team manager at the South Downs Health NHS Trust, said during 2005, more straight people were infected with HIV than gay people but most caught the virus abroad.

She said the authority was trying to make people think of HIV the way they would think of heart disease or cancer, as a long-term illness rather than a disease that leads to death within a few years.

Anyone concerned about sexual health can call Brighton's Claude Nichol Clinic on 01273 664721 or visit www.swish.org.uk .