Almost half of men who pay for sex already have a partner, reveals a small survey reported in the journal Sexually Transmitted Infections.

The authors used survey data from a standard health screening questionnaire completed by more than 2500 men at one sexual health clinic between October 2002 and February 2004.

One in 10 of the men said that they had paid for sex. Their average age was 34.

Most said that they had paid for sex with women, and over half said that they had paid for sex while abroad. But four out of 10 said they had paid for sex locally.

Just under 2% said they had paid for sex both in the UK and abroad.

Two thirds said that they had paid for sex in the preceding year, and around one in four said that they repeatedly used prostitutes. But the time frame ranged from 2 days to 30 years previously

Almost half (43%) said that they had a current partner when they had paid for the sex.

And more than half (56%) who said that they had had unprotected vaginal sex already had a partner.

Unprotected vaginal sex was more common among those who paid for sex while abroad, but unprotected oral sex was twice as common among the men who paid for sex locally. Unprotected oral sex can facilitate transmission of infection, the authors point out.

Although none had HIV infection, one in five had a sexually transmitted infection, including gonorrhoea, Chlamydia, and syphilis.

The authors suggest that the figures may be an underestimate of actual behaviour as some men may choose not to reveal whether they have paid for sex.