MARK COLVIN: The New South Wales Police Integrity Commission has opened an investigation into agreements between the police force and the Catholic Church which may have enabled the church to conceal information about child sexual abuse.

Last year, the ABC revealed details of a draft memorandum of understanding between the police and the Catholic Church.

There was also a special arrangement that saw a police officer sit on an internal church panel in charge of handling child abuse allegations against the clergy.

The Police Integrity Commission has launched Operation Protea to look at whether there was any police misconduct as a result of any agreement to cooperate with the church.

Emily Bourke reports.

EMILY BOURKE: Exactly 12 months ago, the ABC's Lateline program reported accusations that the Catholic Church tried to strike a formal agreement with New South Wales Police over how to handle allegations of child sexual abuse and what information would be handed over for investigation.

There are questions over whether this memorandum of understanding was ever signed, approved or even in operation.

Now, the NSW Police Integrity Commission has set up an inquiry to investigate such arrangements and whether there was any police misconduct between 1998 and 2005.

It will also look at the secondment of a police officer to an internal church committee which dealt with allegations of child abuse by clergy.

DAVID SHOEBRIDGE: Well this is a very welcome announcement. It is clearly a matter of deep and serious concern to the integrity commission. The fact that they're holding a public hearing is further confirmation that this is a serious inquiry, but it needs to go to the highest levels of the NSW Police.

EMILY BOURKE: NSW Greens MP David Shoebridge accessed the police documents under Freedom of Information more than a year ago and he's been campaigning for an independent inquiry.

DAVID SHOEBRIDGE: At the core of this investigation is a private arrangement between the NSW Police and the Catholic Church that saw a senior NSW Police officer sitting on an internal church body. And in the course of that, being given volumes of evidence about individual cases of criminal child sexual abuse.

EMILY BOURKE: He says the documents he's obtained raise serious questions.

DAVID SHOEBRIDGE: It became apparent that there was a formal memorandum of understanding between the police and the church we saw this police officer engaged on the internal church committee. And then when we asked for the details of the evidence that had been given to that police officer, we were told that there was a protocol in place that either all the evidence was returned by the police officer or anything that was retained by the police was shredded.

Now, how on Earth that came to be is an absolutely extraordinary set of circumstances, a deep potential conflict of interest for the police and is why, I assume, the Police Integrity Commission is taking such a careful view of it.

The problem is, the police are there to investigate crimes, and so when crimes are brought to their attention, their primary obligation must be to investigate the crimes and bring criminals to book. They're not there to provide ad hoc advice to organisations who have individuals within those organisations committing crimes. This is, I think, really the core of the conflict of interest here.

EMILY BOURKE: While it might be argued that such cooperation enabled an exchange of intelligence between police and the church, David Shoebridge says it's difficult to justify such an arrangement.

DAVID SHOEBRIDGE: Well there is a fundamental problem when you effectively coopt the police into your own internal inquiries. And of course, the church has an obligation under the criminal law here in NSW to report to police instances of child abuse that would amount to an indictable crime, and almost certainly, every one of the alleged allegations would have satisfied that obligation to have to report.

And you can only speculate that the church may well have set up this institution and the arrangement with the police seeking to satisfy their reporting obligations under the Crimes Act and therefore avoid prosecution for failing to report to the police.

EMILY BOURKE: The Catholic Church's Truth, Justice and Healing Council says it welcomes the Police Integrity Commission's inquiry. The council says any investigation that can provide greater clarity around the relationship between the police and the Catholic Church in relation to child sexual abuse is welcome and will be fully cooperated with.

The public hearing will be held on Monday 13th October in Sydney.

MARK COLVIN: Emily Bourke.