Fears over gay men practising unsafe sex
More than half of men who recently had sex with another man did not use a condom.
Risky sex is widespread among gay men and also people who are not in committed relationships, the Healthy Ireland survey reveals.
Almost one in six people who are having sex with someone outside a steady relationship used no contraception.
The report said although these represented small groups of the population, the exposure to risk was "significant".
Commenting on the findings, Rory O' Neill, who has HIV and is well-known as drag performer Panti Bliss, said: "I am shocked. I think a younger generation of gay people don't remember the shock and the fear and people getting sick and dying.
"They see a pamphlet about safe sex - it's so removed from their experiences. Young people always think they are invincible, protection is not part of their agenda."
Sex without condoms leaves people at risk of sexually transmitted disease. For women, it increases their chance of a crisis pregnancy.
Overall condom use is highest among those who have recently met (73pc) and lowest among couples who are living together (16pc).
The majority of people (85pc) say they are in a relationship with the person they are having sex with. However, there is evidence that men are more promiscuous than women.
While 88pc of women are in a relationship with the last person they had sex with, this falls to 82pc for men.
Having sex outside a relationship is more common among younger people aged 17-24.
Nearly six in 10 men and four in 10 women has had sex with someone who was not their partner.
Some 12pc aged 17-24 "had only just met" the last person they had sex with.
Around three-quarters of gay men or women who had recent sex were in a relationship, but the rest were not.