Former Victorian police chief Reg Jackson was the architect of a conspiracy to conceal child sex abuse by a Catholic priest, his successor has told an inquiry.
The police and church protected pedophile Monsignor John Day, thwarting a 1971-1972 investigation by former Mildura policeman Denis Ryan, the child abuse royal commission has heard.
Mick Miller, chief commissioner from 1977 to 1987, says he did not know of the existence of a "Catholic mafia", as described by Mr Ryan, comprising Catholic police officers who protected priests.
But he blames his immediate predecessor Mr Jackson for police putting a stop to Mr Ryan's investigation into Day.
"It is my opinion that chief commissioner Reg Jackson was the architect of the Victoria Police's response to Denis Ryan's investigations into Monsignor Day," Mr Miller told the commission on Tuesday.
"It couldn't have operated in the manner it did without his knowledge and consent.
"Everybody down the chain of command ... appears to have fallen into line."
No one spoke to Mr Miller, then an assistant commissioner, about the Day investigation or supported Mr Ryan, the inquiry heard.
"In my opinion this points to Reg Jackson as the only one who could have produced and achieved the final outcome," Mr Miller said.
He said Mr Ryan should be compensated for what he went through and his premature resignation in 1972.
"The driving force behind his crusade was the desire to achieve justice for the victims of a hypocritical pedophile priest," Mr Miller said.
"This entire episode is a shameful event in the history of Victoria Police."
Current Chief Commissioner Graham Ashton says he will apologise to Mr Ryan and discuss compensation.
"We say to the victims of Monsignor Day that Victoria Police made mistakes in the past. We acknowledge that," he told reporters.
Mr Ryan has told the royal commission and written a book about a conspiracy against him to conceal the crimes committed by Day, a priest he caught with his pants down in a car with two prostitutes in Melbourne in 1956.
Mr Ryan said he was told to drop his abuse investigation into Day and forced out of the police force.
"In the early days I had nightmares of Monsignor Day raping kids and the way the police force had condoned these offences," Mr Ryan said.
"Those children were being mentally and physically destroyed by Day and the police protected him."
He said then Ballarat bishop Ronald Mulkearns also protected Day.
Fifteen people have made child sex abuse claims against Day to the church, all after his death in 1978.
The inquiry also heard from a man who believed the Christian Brothers paid off his parents after his brother was abused by Brother Edward Dowlan at Ballarat's St Patrick's College in 1973.
BWF, who was 14 at the time, said he told then Ballarat priest Cardinal George Pell that Dowlan had beaten and molested his brother and demanded to know what he would do about it.
"Pell became angry and yelled at me: 'Young man, how dare you knock on this door and make demands'," BWF told the commission.
Barrister Sam Duggan said Cardinal Pell was living at a different Ballarat presbytery at the time and suggested BWF made the story up, which he denied.