The South Australian Catholic Church says it has been blindsided by news that clergy will have to report child abuse revealed to them in the confessional.

Key points: The confessional will no longer by exempt from mandatory reporting of child sex abuse

The confessional will no longer by exempt from mandatory reporting of child sex abuse Catholic priests are not allowed to divulge confessions under canon law

Catholic priests are not allowed to divulge confessions under canon law Catholic Church unaware of changes coming in on October 1

From October 1, South Australia will become the first state where priests will be legally obliged to report any confessions of child sex abuse.

If they don't they could receive a $10,000 fine.

Acting Archbishop of Adelaide Greg O'Kelly said the church was "unaware of this change" until today "and the implications are now being considered".

New child protection laws passed last year — but made public today by the state's Attorney-General — removed an exemption for priests from mandatory reporting when the information was divulged during confession.

Attorney-General Vickie Chapman revealed the change ahead of the State Government releasing its full response to the Royal Commission into Child Sex Abuse.

While priests have been mandatory reporters outside of confession for more than a decade in South Australia, Bishop O'Kelly said the new law "has much wider implications for the Catholic Church and the practice of our faith".

Greg O'Kelly is Bishop of Port Pirie and acting Adelaide Archbishop. ( Australian Catholic Bishops Conference )

Priests are bound by the seal of the confessional to not reveal what they are told or face automatic excommunication.

"Our commitment in South Australia to child protection and child safe environments is unwavering," Bishop O'Kelly said in a statement.

"Our priests are well aware of their obligations to report child abuse and neglect under mandatory reporting laws and have been participating in regular and compulsory child protection training since 2007, as have all our church employees and volunteers."

Other states urged to follow in SA's footsteps

Ms Chapman said mandatory reporting was so important, including in confession, because abuse usually occurred in secret "unless a responsible adult acts".

"The protection of children the public expect must be superior to any other interest," she said.

Ms Chapman said other states should follow South Australia's lead.

"Unless you have a unified approach to this, predators will travel, that is the reality," Ms Chapman said.

"They'll find sanctuary in areas where they can't be caught and it is important that there be a disclosure obligation at all fronts and you don't leave some frontier of sanctuary for those who are going to predate."

When asked on ABC Radio Adelaide this morning how a priest would be caught breaking the law, Ms Chapman said it would be similar to other mandatory reporting failures, in that it would most likely be revealed if the accused admitted telling a priest.

South Australia's response to the Royal Commission

The State Government plans to remove statutory time limits that prevent victims from suing the institutions where they were abused.

"In essence, at the moment, when a child turns 21, they can't make a claim after that age — that is three years after they're 18," Ms Chapman said.

"We want to remove that for all child sex abuse victims."

Port Pirie Bishop O'Kelly was named Apostolic Administrator of the Adelaide Archdiocese earlier this month after Archbishop Philip Wilson became the most senior Catholic to be convicted of concealing child sex abuse.

A magistrate said he did not accept Wilson could not remember a 1976 conversation, in which a victim described his abuse at the hands of priest Jim Fletcher.

Ms Chapman said he would have already been obliged to mandatory reporting in South Australia since he was told by a victim.

About 300,000 South Australians are Catholic, according to the Census.