A Special Commission of Inquiry into allegations of a cover-up of child sexual abuse claims in the Catholic diocese of Maitland-Newcastle has released findings that are damning of the man who claimed to blow the whistle.

The four-volume report, three volumes of which have been released by Commissioner Margaret Cunneen SC, uncovered no evidence to show that senior police ever tried to ensure child abuse offences were not properly investigated.

One confidential volume contains findings that may lead to criminal charges being laid against a senior Catholic Church official.

The inquiry found Detective Chief Inspector Peter Fox was not a credible witness and that it was appropriate for senior police to instruct Chief Inspector Fox to cease his own investigations.

"The commission finds no credible evidence to support the notion that there are senior police in Northern Region Command of the New South Wales Police Force, including Newcastle City Local Area Command, who were prepared to take steps to try to ensure that alleged child abuse offences involving Catholic church officials were not investigated or not properly investigated," it found.

"The commission considers that by at least 2010 Fox had lost the objectivity required of an investigating officer regarding such matters.

"While he remained passionate about things involving the Catholic Church, he no longer possessed the detachment necessary for properly investigating such matters. In short, he had become a zealot.

"Fox's evidence should be approached with caution, Fox gave evidence to the commission that was implausible.

"Fox was also prone to exaggerate aspects of his evidence.

"Fox's lack of objectivity in connection with matters involving the Diocese and related police investigations was such that the commission took the view that, on matters of controversy, Fox’s evidence must be approached with caution."

The commission also questioned Fox's integrity surrounding the inquiry, questioning his decision to provide police information to a journalist.

"The commission formed the view that Fox had engaged in conduct that was inconsistent with the integrity required of a police officer," the report said.

"He provided sensitive information about police investigations (including an internal police report and a victim's statement) to a journalist, [Fairfax reporter Joanne] McCarthy."

The report has also found that senior church officials did have information relating to child sexual abuse in the area that would have assisted a police investigation.

It named Bishop Leo Clarke, who was head of the diocese for 20 years.

It says his conduct in failing to tell authorities about one priest was "inexcusable" and that he was motivated by a fear it would bring scandal on the church.

"A substantial body of evidence before the commission confirmed that senior Diocesan officials were aware at various times of reports or complaints that [Father Denis] McAlinden had sexually abused children, the first instance of reported abuse occurring in 1954 and involving victim AE," it said.

"It took more than 40 years however for the Diocese to report to police any aspect of McAlinden's offending history.

"The evidence reveals a disturbing story of repeated inaction and failure on the part of church officials to report McAlinden to police."

Two inquiries announced

The trigger for the inquiry came in November 2012 when Detective Chief Inspector Fox spoke out about "the evil of paedophilia within the Catholic Church", alleging cover-ups by the church and police.

The veteran detective had written to the premier and then aired his claims on the ABC's Lateline program.

Sorry, this video has expired Watch Lateline's interview with Peter Fox from November 2012

Chief Inspector Fox alleged he had been directed by police to hand over his files and ordered to cease an investigation into child sexual abuse by members of the Catholic clergy.

The detective claimed his evidence related to the investigations into the crimes of two now-dead paedophile priests, Father Denis McAlinden and Father Jim Fletcher.

Within days then-premier Barry O'Farrell announced the Special Commission of Inquiry and shortly afterwards then-prime minister Julia Gillard established a royal commission.

The inquiry sat for 92 days of public hearings, mainly in Newcastle, where 50 victims and their families gave evidence.

All up 161 people appeared before the commission, giving evidence in public and private hearings.

Witnesses included several New South Wales police officers and two Catholic bishops who publicly apologised for the church's handling of child sexual abuse over half a century.

I felt more like a criminal: Peter Fox

Chief Inspector Fox said he stood by his evidence to the Special Commission as well as allegations he made earlier on the Lateline program in 2012 and in a letter to the NSW premier.

"They are the two things that triggered everything and I don't think anywhere through the Special Commission anything that I said in those documents has been cast into any sort of doubt," he told Lateline after the report was released.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 6 minutes 40 seconds 6 m Detective Chief Inspector Peter Fox says he stands by his claims.

Chief Inspector Fox is currently overseas but in an earlier statement issued to the ABC he criticised Mr O'Farrell's decision to continue with the NSW Special Commission when the Federal Government decided on a Royal Commission.

"Throughout the Special Commission I felt more like a criminal on trial than a witness as hostile treatment continued over an unprecedented and oppressive 14 days of repetitive cross-examination leaving me to question its purpose," it said.

"I believed the central issue for the Special Commission should have been the future protection of children, but that somehow appears to have been misplaced.

"Conversely my treatment by the Royal Commission has been exemplary.

"Numerous survivors and support organisations have echoed my own experience.

"I am at a loss as to what the Special Commission attained that could not have been achieved by the Royal Commission.

"In time that may become apparent. However, after the example of my ordeal I can only imagine the effect on others who might have contemplated coming forward.

McCarthy welcomes prospect of prosecution

The Newcastle Herald journalist credited with first exposing the protection of paedophile priests in the region, Joanne McCarthy, told Lateline she is pleased the commission found there is sufficient evidence to charge a senior Church official for protecting Fletcher.

She said the finding was internationally significant.

Space to play or pause, M to mute, left and right arrows to seek, up and down arrows for volume. Watch Duration: 12 minutes 22 seconds 12 m Joanne McCarthy welcomes the key findings of the Special Commission.

"There have been less than a handful of prosecutions for concealing matters relating to clergy, so we're not talking about the perpetrators here, we are talking about people who might have had knowledge of perpetrators," she said.

"It is also significant, I think in this region, because we have been writing about really serious child sex abuse involving Catholic clergy since 1995 and in so many of these cases, in fact virtually all of them that I am aware of, there has been evidence of Church knowledge of those perpetrators."

However, McCarthy said she agreed with the Special Commission that Chief Inspector Fox had lost objectivity.

She told Lateline some of his allegations were not borne out by the evidence but said she had sympathy for his predicament.

"You're dealing with really serious offences - distressing, devastating offences - against children," she said.

"You work in that area for too long, you get views about it and it is easy to lose objectivity. I am not making any excuses for that but I certainly do understand how it can happen.

"Peter Fox is certainly paying the price for caring too much and I think that is why he retains really strong support from the public."

McCarthy said she was disappointed at the way she was treated by police during the commission and their response to the abuse allegations.

"Certainly they were very happy to smash my name around when it suited them, knowing that I wasn't in the terms of reference, so for a lot of that inquiry I was trying to stand up for myself with one and a half hands tied behind my back," she said.

Victims stand by Peter Fox

Pat Feenan, whose son was abused by Father Fletcher, is standing by Chief Inspector Fox despite the findings, calling him a man of integrity.

"Personally I've found Peter Fox very, very credible," she said.

"On our journey we have found Peter Fox to be a man of great integrity and that will stay with our family."

Pat Feenan's son Daniel was sexually assaulted by a Hunter Valley priest. ( ABC News: Dan Cox )

She says the findings that the church failed to act have come as no shock.

"I don't think there is any surprise there. How disappointing," she said.

"A victim said to me it's bad enough that it happened but it's compounded by cover-ups, the perpetrators, the whole thing being ignored.

"It made it so much worse because this is the Catholic Church we are talking about, that's not what you expect.

"But I'm not surprised about that. It's what we long suspected."

Peter Gogarty, one of Father Fletcher's victims, says a lot of people in the Catholic Church knew about the abuse.

"There's certainly vindication for a lot of people like me that people in the Catholic Church, contrary to their long-stated position that they knew nothing, a lot of those people in the Catholic Church knew about activities of Catholic priests for a long, long time," he said.

"Those priests were assisted in their crimes by virtue of the fact that other people knew about it and did nothing, so I feel very vindicated."

Premier and police to consider findings

New South Wales Premier Mike Baird says he is satisfied with the findings.

"I thank Commissioner Margaret Cunneen SC who conducted the inquiry, which was designed to ensure allegations surrounding child sexual abuse in the Hunter were fully investigated," he said.

"The four-volume report was delivered to the NSW Governor [Friday] morning and the first three volumes have now been released by the NSW Government.

"The commission has recommended that the fourth volume of the report remain confidential at this time.

"The NSW Government will consider the commission’s report and respond in more detail in due course."

The New South Wales Police Force has also welcomed the report and says it will also take time to read the findings.