Police Association president Greg O'Connor says most complaints made against the police are from "perennial complainers who complain about everything to everyone".
Last night's episode of The Vote tackled the subject of trust in the police, and by the show's end 56 percent of viewers said they were losing trust in the force.
Much of the blame has been placed on the perceived lack of independence in the so-called Independent Police Conduct Authority (IPCA).
Appearing on Firstline this morning, Mr O'Connor defended figures showing the authority only investigates 5 percent of the complaints it receives.
The IPCA received almost 2000 complaints last year. Of these, only 57 percent were looked into – mostly by police themselves – and only one in 20 were investigated by the IPCA.
"Many of those complaints are frivolous," says Mr O'Connor. "Many of them are made by perennial complainers, and anyone watching the show who works in a government department will know that they've got the perennial complainers who complain about everything to everyone.
"They are the ones that fortunately for the public, are not investigated."
There are also concerns the investigations that do take place are compromised by the IPCA's reliance on former police officers.
Barrister Marie Dyhrberg says IPCA chair Sir David Carruthers has asked for investigators from different backgrounds.
"He wants more independence, he wants the perception that people can go to the authority," she says. "Why would you go to the authority if it's just going to be kicked back to the police?"
Mr O'Connor says former police officers are the best choice, as not only are they trained in investigations, but only they can break through the "wall of silence" that would block investigators from a different background.
"All we want is good investigators. I've seen some of the worst inquiries done by lawyers who are not trained investigators – they're trained lawyers.
"The reason he uses ex-police is that they are actually trained investigators."
He points to survey figures showing 79 percent of Kiwis have "full trust and confidence" in the police and dropping crime rates as proof the current system is working.
"[The IPCA] must be impartial and thoroughly considered in its work, and with Sir David Carruthers in charge, I would defy anyone to say it is anything other than impartial and thoroughly considered. He is a very professional ex-judge."
But Ms Dyhrberg says there's plenty of room for improvement – including giving the IPCA greater powers.
"At the moment it can only recommend, and the police do not need to follow," she says. "They lack the power to really bring about reform, to bring about good investigations on their own initiative."
An internal police survey brought up on The Vote last night said 36 percent of police don't feel they can make a complaint about inappropriate police behaviour because of the backlash they might face.