The Police Minister says the Wally Haumaha inquiry was necessary to maintain the public's trust and confidence in the Police.

The report, which was released yesterday, found Police Commissioner Mike Bush knew Louise Nicholas had raised concerns about Wally Haumaha in the past - but did not raise the issue during the appointment process for the deputy commissioner role as he thought it had been resolved.

That decision was reasonable in the opinion of Mary Scholtens QC, whose report cleared the appointment process of any fault.

Stuart Nash told Mike Hosking the report was crucial because the public needs to trust the process used to appoint high-level police officers.

"This is a very important position in the state sector. This is sort of the number two police officer and we have got make sure we get it right and in terms of earning the public trust and confidence in police the public need to be sure."

He said the concerns raised by Louise Nicholas also needed to be investigated.

"She's a very well-respected advocate [and] you could argue, that in fact, Louise Nicholas coming forward in very trying circumstances was the single most important catalyst for culture change in the Police. Now that's a big call but she's played a very important part in changing the culture."

The Police Minister said the report was focused on making sure the correct process was followed. 

"Was the process efficient? Was the information that was provided to the panel who were recommending DC Haumaha sufficient? And Mary Scholtens has come out and said, 'yes it was'."

When asked by Mike Hosking how much the inquiry cost, Nash said, "I'm not too sure".

He said the bill wasn't the important thing.

"The important thing is that the public has trust that the confidence to appoint our top public service is the right one."

LISTEN ABOVE AS STUART NASH SPEAKS WITH MIKE HOSKING