Inspector Fox, the first witness on day one of the inquiry into the alleged cover-up of child sexual abuse by priests of the Catholic Diocese of Maitland-Newcastle, revealed there were members of the police force dubbed - "the Catholic Mafia" - who hindered investigations into abuse.

He told the inquiry, that rather than following official police procedure he began his own investigations in about 2010. "I didn't trust the police environment at this stage," said Inspector Fox who began emailing documents to his personal account: "I had become very concerned about the police handling of the investigation and wanted as many of the documents as I could."

When he returned from a month's leave in 2012, Inspector Fox was told by a now retired public servant that his office had been search by two senior police who were looking for documents regarding the Catholic church.

"She said: 'Don't tell anyone but [they] came up here and asked for the key to your office, they searched top to bottom, looking in every filing cabinet'," Inspector Fox said.

 "They asked if she knew if I was investigating the Catholic church. I was afraid something like that would happen, I started to distrust very senior police about what was happening."

His repeated pleas to establish a task force looking into the sexual abuse by several members of the Maitland-Newcastle diocese, he said, fell on deaf ears and he was formally removed from further investigations in 2012.

 That year, Inspector Fox spoke to ABC TV's Lateline program where he accused the Catholic church of a cover up.

 These allegations sparked the inquiry that will for the next two weeks focus on priests - Father Denis McAlinden and Father James Fletcher, both dead.

Counsel assisting, Julia Lonergan SC told the inquiry McAlinden, who perpetrated sex crimes in Maitland over four decades, was labelled a predator by a former Bishop. Fletcher was convicted of his crimes in 2004 and died in jail two years later.

Inspector Fox will continue his evidence today.