Five police officers have lost their jobs and 20 have been formally disciplined for using the police national database to snoop on law-abiding New Zealanders.
Figures released to the Herald on Sunday under the Official Information Act show that, as of January 30 this year, a further seven staff had resigned before police took disciplinary action. Another case is still under investigation.
The revelations have sparked calls from Privacy Commissioner Marie Shroff for tighter controls to stop prying police using the database for non-police business.
She was unsure as to exactly why police officers would access confidential files, but said it could be a case of an officer wanting to find out about a potential business partner, or their daughter's new boyfriend.
"I doubt there is anything particularly sinister here."
Nevertheless, she was disappointed officers would abuse the "implicit social contract they had with the public" by improperly accessing the national database.
Private investigators said they believed officers were often asked for information by firms looking into the backgrounds of individuals.
In some cases, private investigators would pay officers "under the table" for information that could assist with their inquiries, one investigator told the Herald on Sunday.
Another, Auckland private investigator Lew Proctor, said: "It's not something we do, but I have no doubt that it goes on."
Police would not give details about each case, but said clear policy guidelines stated a person's file could be accessed only for "legitimate police purposes and not for private purposes".
Most cases came to the attention of police as a result of complaints from people whose files had been accessed, while others were a result of monitoring database use.
But Shroff suspected abuse could be far more widespread. She believed most cases would go undetected because it was probably only in rare circumstances someone would ask who had accessed their personal information.
The latest revelations came two years after thousands of sexually-explicit images were found on police computers.
The pornography scandal was uncovered during a wide-ranging probe of police culture sparked by a string of damaging controversies three years ago, including the Louise Nicholas rape case and the botched handling of a 111 call from Auckland model Iraena Asher.
Shroff said the latest controversy would undermine the credibility and public trust in the police. She was working with police on a new system to prohibit "unauthorised browsing".
"We want to make sure the database isn't used improperly by police officers.
"Hopefully, we can get a system in place that will enhance trust in the police," she said.
* Verbal warning: 10 officers.
* Written warning (non-sworn): Five officers.
* Adverse report (sworn): Three officers.
* Disciplinary charges (sworn): Two officers.
* Dismissal: Five officers.
* Resignation before disciplinary action: Seven officers.
* Currently under investigation: One officer.