MORE than one in 20 Victorian Catholic priests became a child abuser and the church's senior leaders may have to go to jail for covering up the crimes, a former priest and academic has told a state inquiry.

On the second day of public hearings into churches' handling of child abuse, RMIT intercultural studies professor Des Cahill said the Catholic Church had created a "holy and unholy mess" it was incapable of taking action to resolve.

A former priest who, when resigning in 1976, accused the Catholic Church of being unable to face up to its problems, Prof Cahill warned the inquiry the State Government needed to intervene.

"It is an unfortunate reality that as a result of this inquiry some senior religious people may end up in jail for dereliction of duty, and they must be treated with compassion and understanding," Prof Cahill said.

"But children matter.

"Abused children matter very much and their mothers' cries are beseeching heaven.

"I pray that you will hear them."

Prof Cahill said that based on his analysis of priests in the archdiocese of Melbourne who trained at Corpus Christi College between 1940 and 1972, about one in 20 ordained priests in Victoria and Tasmania became child abusers.

"I remain comfortable with that figure and the incidence is much higher than in the general population and much higher than for any other professional group," Prof Cahill told the parliamentary inquiry.

"The one in 20 is a minimum - it may be one in 15, perhaps not as high as one in 10."

After hearing Prof Cahill's claims that churches of many denominations were unable to take responsibility for child sexual abuse, the parliamentary committee heard evidence about the success of mandatory reporting in the child-protection sector.

Department of Human Services secretary Gill Callister told the committee there were now 230,000 Victorian professionals required by law to report any suspected instance of child abuse.

While mandatory reporting is increasing reports of at-risk children, Ms Callister said the process was focused on protecting children from harm at the hands of their carers and not institutional organisations.

She said it was a complex matter about whether mandatory reporting would work in an institutional setting, but "we shouldn't have a situation where children can be at risk of abuse ... and not have a effective system to protect them".