Life insurers are asking people seeking insurance if they have sex with prostitutes.

The Privacy Commission has raised concerns over the issue, and says anyone who has worries about questions they are asked can complain to the Privacy Commissioner.

Companies which ask about their clients' sexual behaviour with prostitutes include BNZ bank and AMP insurance. Those which don't include Westpac, Kiwibank and AA Life.

IAG, the parent company of NZI and State Insurance, and ASB Bank did not respond.

AMP chief underwriter Geoff Dyer said the company asked everyone applying for life insurance if they were aware of being exposed to HIV. This included whether they'd had sex with, or as, a prostitute.

The question had been asked in this form since 2004, but a similar question had been asked since Aids and HIV were identified as major health issues, Mr Dyer said.

"We ask this question as people who are in what is considered "at risk" sexual practices are at greater risk of acquiring HIV/AIDS than those that aren't."

Other commonly asked life insurance questions include whether a person has ever had a sexually transmitted disease, raised cholesterol or a bowel polyp or has ever attempted suicide.

Investment Savings and Insurance Association chief executive Vance Arkinstall said insurers had to ask personal questions to be sure they were understanding the risk with each person's policy.

"There are delicate questions," he said. "Companies ask them in different ways and it is just part of assessing what the risk is.

"Some companies will have different views, but there are concerns over sexual preferences of people from time to time and it's born out of the risk of Aids and those sorts of issues.

"Some people do find the questions difficult to answer and in that situation, if you're uncomfortable, well, there are a lot of insurers - go and try another one."

Assistant Privacy Commissioner Katrine Evans said anyone who felt they had been asked intrusive or irrelevant questions could complain to the commissioner.

"Questions asked by life insurance companies should not be unreasonably intrusive and must be directly relevant to assessing risk," Mrs Evans said.

'Some illnesses can have a significant impact on whether a person is insurable, or at what premium.

"It's not immediately obvious, though, that the nature of sexual partners or activities is relevant. Insurers would have to be able to justify this very carefully."