Gay men’s health charity GMFA has launched a campaign to warn gay men they cannot guess whether their partner will be HIV-positive.

According to the charity, studies have shown that around 40 per cent of HIV-negative men who claim to know their sexual partner’s HIV status are actually guessing. Research suggests that only 20 per cent of HIV-positive men say they always disclose their status, while it is estimated that a third of men with HIV do not know they have the virus.

GMFA has launched a campaign which features a video of a man using a fantasy ‘HIV detector’ to tell whether the man he is trying to pick up is positive or negative.

Another part of the campaign will be postcards in London gay bars with messages such as ‘How do you know his HIV status?’ and encouragement to use condoms.

Matthew Hodson, head of programmes at GMFA, said: “Lots of gay men believe that they can always tell the HIV status of their partners just by looking at them, or by where they meet or the sex that they’re into.

“The truth is that there are HIV-positive and HIV-negative men, of all shapes and sizes, in every city and in every gay venue across the country.

“Guesswork won’t keep you and your partners safe. Using a condom remains the best way to prevent the spread of HIV.

“The video is based on our previous ad campaign and we hope that it gets the message across in a way that’s a bit fun and a bit quirky.”

To see the video, click here. Postcards can be downloaded here.