Former police officer turned private investigator Grace Haden supports Auckland Mayor Dick Hubbard's call for police to start using non-sworn investigators.

Mrs Haden said she had noticed disturbing trends since she left the force 16 years ago to have a family - trends that could be reversed with the use of non-sworn investigators.

The former sergeant, who owns Verisure Investigations, said one in five offences did not make it to investigation level but hiring PIs would help to change that statistic.

She said the problem was so bad that many complaints were not even recorded by police any more.

"Policing is statistics-based, so if you can avoid taking complaints then reported crime goes down and policing looks more effective," she said.

"Crime has been re-classified. Many things are now called civil and complaints are turned away at the public counter."

Mrs Haden said it had become extremely difficult and time-consuming to report offences so many people did not bother.

She said private investigators would need access to police resources to work on cases. At the moment they only have the same resources as members of the public.

She outlined several cases she handled as a private investigator that police had turned away:

* A man had his car stolen but when he reported it to police he was told it was a civil matter. After a private investigation and three trips to the police station, the complaint was finally taken. The offender was located in Wellington and was charged and convicted.

* A fraudulent dealer on the TradeMe website set up accounts in different names, traded in small items to get her ratings up, then sold cameras and telephones that did not arrive. Police failed to take the complaint, saying it was a civil case.

* A woman gave evidence on oath before a tribunal that was later proved to be false. A complaint was made to police in writing and police wrote back to say it was not perjury and they would not investigate.

* A woman defrauded her boss by stealing $60,000 of goods but police would not investigate. The company employed Mrs Haden to prove the matter. The completed investigation was passed to police and the offender is before the court.