The Catholic Church in Victoria revealed the number in a submission to a state parliamentary hearing on Friday but said the instances of abuse reported had fallen dramatically from the "appalling" numbers of the 1960s and 1970s.
"It is shameful and shocking that this abuse, with its dramatic impact on those who were abused and their families, was committed by Catholic priests, religious and church workers," Melbourne Archbishop Denis Hart said.
The full submission was not released publicly but the church said most of the 620 claims it had upheld over the last 16 years related to incidents 30 to 80 years ago, with very few related to abuse that has taken place since 1990.
Hart said the church had taken steps to redress the issue, including a programme implemented in the 1990s involving an independent investigation, an ongoing programme of counselling and support, and compensation.
"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," he said.
But victims' supporters say the number of children abused was likely much higher than that confirmed by the church in its own inquiries.
President of the Law Institute of Victoria, Michael Holcroft, said there was a need for more independent investigations.
"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," he told the ABC.
The Victorian state government announced the inquiry into the handling of child abuse cases by religious and non-government bodies after the suicides of dozens of people abused by clergy.
Last year Pope Benedict XVI told Australian bishops that their work had been made more difficult by the clerical sex abuse scandal which has rocked the church as he exhorted them to "repair the errors of the past with honesty".
The pontiff met victims of abuse when he travelled to Sydney in 2008. – Sapa-AFP