The Law Institute of Victoria is calling for the establishment of an independent authority to examine how religious organisations respond to cases of child sex abuse.

It comes as the Catholic Church in Victoria revealed at least 620 children have been abused by clergy since the 1930s, in a submission to a state parliamentary inquiry.

It is the first time the church has publicly released the figure.

The Law Institute's president, Michael Holcroft has told AM its submission to the inquiry is also pushing for a royal commission into church sex abuse and for the reporting of such incidents to be strengthened.

But he says the committee does not have the powers, resources or time to do a thorough review.

"The hard one of course is in the Catholic Church, with the situation with confessions," he said.

"What we've said is look, we believe there needs to be a balancing [act]. If it's a confession that would protect children going forward, that someone is saying 'I've got this problem, and I'm continuing this activity', then that is something that should have to be reported to the police.

"Obviously there's a public perception that the church investigating the church is Caesar judging Caesar and I think that the community is now looking for somebody external, someone independent to get to the bottom of what's obviously been a big problem for a long, long time."

Church challenged

Chrissie Foster's two daughters were abused by a priest in the 1980s and she says the number of victims is likely to be much higher.

She says she can't understand how the church can say it is open, when it's taken a parliamentary inquiry to force this issue.

"It's only been victims coming out and going to the police that has stoped all of this. The church has never lifted a finger to stop their paedophile priests," she said.

"To remove them, to laicise them. Nothing. They have just moved them on to new children and there are new victims."

And she says the number of abuse victims confirmed by the church is far too low.

"Apparently the average number for peodophiles in general in their lifetime is about 110, so you're looking at about 10,000 or so."

In its submission to the inquiry, the church revealed the cases of criminal child abuse have been upheld by its own complaint procedure.

It says the cases go back 80 years, but the vast majority relate to abuse in the 1960s, 70s and 80s.

On Friday, the Catholic Archbishop of Melbourne, Denis Hart, said the church would cooperate fully with the inquiry.

"In [the submission] Facing the Truth, we have been open about the horrific abuse that has occurred in Victoria and elsewhere," he said.

"It is shocking and shameful that this abuse, with its dramatic impact on those who were abused and their families, was committed by Catholic priests, religious and church workers.

"This submission shows how the church of today is committed to facing up to the truth and to not disguising, diminishing or avoiding the actions of those who have betrayed a sacred trust."