An Auckland policewoman who boosted her income moonlighting as a prostitute in a top massage parlour will have earned up to $500 a night.

She worked in a "very classy brothel" that employs several attractive women and was well taken care of by management, a spokeswoman for sex workers said yesterday.

Police said the officer, who would take home at least $43,000 a year from the force, did not ask permission to take a second job but if she had, approval would not have been granted for sex work.

It is understood financial difficulties led her to find a second job, but the Police Association has condemned her choice of work.

The policewoman has not been identified but works in the Auckland City district, where female officers make up around 20 per cent, or 132, of the 660 sworn staff.

Deputy Commissioner Lyn Provost said the officer worked "for a limited time" as a prostitute before this was discovered this year.

Police would not comment on how they found out about the prostitution but said it was treated as an employment matter.

"I can assure the public that police have acted properly in this matter and that this type of secondary employment would never be approved given that the type of work is inappropriate and incompatible with policing," Mrs Provost said.

The policewoman had the support of the New Zealand Prostitutes Collective, said Auckland manager Annah Pickering. "Everyone has to make some sort of living. If she had to pay off certain debts, by all means we totally support that person."

Police Association president Greg O'Connor said there was sympathy for the situation which led to the woman's sex work.

"But it doesn't change the fact that instinctively police officers know this is not right."

Mr O'Connor said the association was "very uncomfortable" with the woman's choice of work. "It's still regarded as a twilight industry that is a major conflict of interest with what we do as police officers."

Many police officers struggled financially, especially in the major cities, and more and more sought secondary employment, Mr O'Connor said.

Ms Pickering said sex workers came from all walks of life.

"We have had law students, doctors, students, and I don't think there's anything wrong for a police officer to be a sex worker."

She would not identify the parlour that employed the policewoman but said it was "very classy".

The parlour did not have any connection to gangs or organised crime, she said.

"It's probably one of the top brothels in Auckland. On a night ... [she would have made] about $500."

Some sex workers at the parlour were aware the woman was a police officer but they were not concerned. However, the majority were did not know of the woman's other work.

"Anyone who does enter the industry does have a second identity so that would have been her own choice of disclosure," said Ms Pickering.

"Most people ... in the sex industry wouldn't disclose information about their personal lives. The only thing they backchat about with each other is if that lady was getting more jobs than the other person."

Ms Pickering believed the officer's motive for working in the parlour would have been "purely financial".

Brian Le Gros, owner of The White House and associated massage parlour Monica's in Auckland, would not say if the woman had worked for him.

"I wouldn't say either way because it's not fair to her. It's not fair to anyone. Obviously she didn't want anyone to know, going by the situation, then I wouldn't [say if she worked for him]."

Mr Le Gros said he would consider hiring a policewoman.

"If a lady came along and said she wanted to do parlour work on Friday and Saturday nights but please keep it quiet [because] I'm a policewoman, I'd go, 'OK love, it's OK'."

He supported police opposition to sex work as secondary employment, saying people would not want officers "being tied up at night in parlours".

A manager at Emily's 8 parlour in central Auckland said prostitutes worked under aliases and "what they do in their own time is what they do in their own time".

Police officers can apply to take a job outside the force but must get approval first before undertaking secondary employment.

"In this case no such approval had been sought," said Mrs Provost.

"When this matter came to light it was felt appropriate it should be dealt with under the secondary employment framework.

"The officer concerned has been counselled. Under police procedures this amounts to a censure."

New Zealand First MP Ron Mark questioned whether police needed to tighten the rules surrounding secondary employment.

Police said there were no plans to review guidelines.

Mr Mark said he was also concerned that gangs and organised crime had a large investment in massage parlours, and the woman could have been exposed to blackmail or extortion.

Ms Pickering rubbished Mr Mark's claim of links between criminals and parlours. "There are no brothels in Auckland that are gang-connected or run by gangs."

The female officer who worked as a prostitute was not the first case of police rubbing shoulders with the sex industry.

The relationship between porn king Steve Crow and Sergeant Gaylene Rogers was investigated by police in 2003.

Mr Crow had criminal convictions for distributing objectionable material and the inquiry was treated as an employment issue.

Police are told not to associate with people with a criminal history.

"They really went into it in detail and came back and said it was OK," Mr Crow said yesterday from Sydney.

The couple married six weeks ago.

Secondary work approved by the police includes:

Aerobic teacher.
Guide (fly fishing).
Starter's assistant (racing).
Vessel skipper.
Poll clerk.