EMMA ALBERICI, PRESENTER: The Catholic Church in Victoria has revealed that its clergy were responsible for hundreds of cases of child sexual abuse over the past 80 years.

In a submission to a Victorian parliamentary inquiry, the church admitted that over the past 16 years its internal complaints system upheld 620 claims of child abuse dating back to the 1930s.

But some are asking why it's taken so long for the Church to go public.

Hamish Fitzsimmons reports from Melbourne.

HAMISH FITZSIMMONS, REPORTER: The Catholic Church in Victoria made a confession which many have wanted to hear.

SHANE MACKINLAY, CATHOLIC CHURCH SPOKESMAN: The failures are many. The failures are largely that we were very slow to take victims seriously, to listen to what they said and what had happened to them, to believe their accounts.

HAMISH FITZSIMMONS: A briefing was held for priests, some of whom were distressed by the announcement.

PRIEST: We're all ashamed. We're shattered, really. Just we hope we can move on and help the victims in some way.

HAMISH FITZSIMMONS: The Victorian Parliamentary Inquiry into Sexual Abuse by Religious Orders came after a report by retired judge Philip Cummins, which called for an independent inquiry that could compel witnesses to give evidence. The Church responded quickly.

DENIS HART, ARCHBISHOP OF MELBOURNE: If the Government chooses to have an inquiry we will cooperate fully. And I believe that in such an inquiry, what we have done in Melbourne and the value of what we have attempted to do will be strongly recognised.

HAMISH FITZSIMMONS: The Church says the numbers it revealed today date back to the 1930s.

SHANE MACKINLAY: One of the things that we do in our submission, which we have called "Facing the truth", is precisely to face the truth of those sort of numbers and the horrific extent and the horrific consequences for each of the victims represented by the numbers.

HAMISH FITZSIMMONS: The bulk of the cases are from the 1960s, 1970s and 1980s, and the Church maintains there's been a massive drop in abuse numbers since.

SHANE MACKINLAY: As we look at the times at that which abuse occurred, we see there's less than 20 in the last 20 years. So, where there was absolutely dramatic and appalling rates of abuse in the 1970s and 1980s, that's dropped off extraordinarily.

HAMISH FITZSIMMONS: Some though believe the real figure is much higher. Judy Courtin is doing a PhD in law on abuse in the Catholic Church, and says research shows only a fraction of people report abuse.

JUDY COURTIN, LEGAL RESEARCHER: We have no idea. All we've got to sort of use is a Victorian Law Reform Commission statistic which says that a maximum of 10 per cent of children who were sexually assaulted will ever report to the police. Generally they will not report as children. It can take the victims or survivors decades, if ever, to report.

HAMISH FITZSIMMONS: Much of the abuse was centred around the regional city of Ballarat, Oakleigh in Melbourne and Sunbury on the city's outskirts. Some are cynical about why the Church has now come forward.

JUDY COURTIN: It's interesting that it has taken the threat, if you like, of a parliamentary inquiry - and certainly in New South Wales, the very big push for a Royal Commission - it has taken that for the Church to finally come up with the stats. We have been asking for those stats for a very long time.

HAMISH FITZSIMMONS: Submissions to the inquiry close today and hearings will start next month.