Adults in Canberra could face up to two years' in jail if they fail to report child sexual abuse, under a suite of legislation ACT Attorney-General Gordon Ramsay will introduce into the ACT's parliament on Thursday.

Ministers of religion will also become mandatory reporters, with no exemption for allegations aired under the seal of confession.

Information from the confessional was already going to be covered under the ACT's mandatory reporting laws come April, with a temporary exemption to expire on March 31.

But a review from Honourable Justice Julie Dodds-Streeton QC concluded that the Catholic church was unlikely to comply with any laws that forced priests to break the seal of confession.

That meant priests who didn't report would not be readily detected or successfully prosecuted.

Canberra-Goulburn Catholic Archbishop Christopher Prowse said while he supported mandatory reporting laws, there could be "no reasonable expectation" that forcing priests to break the seal of confession would make people safer and urged the government to reject the new measures.

He said even the review found doing so was unlikely to result in many detections of, or successful prosecutions for, either child sexual abuse or breaches of the reporting obligation itself.

But Justice Dodds-Streeton also pointed out it would not be impossible for a priest to be found out, and Mr Ramsay - a former Uniting Church minister - said they would press forward with the confessional clauses.

"As Attorney General of the ACT I must reiterate that we cannot compromise the safety of our children in relation to the confessional seal. No expression of any faith can put children at risk," Mr Ramsay said.

Anti-child abuse campaigner Damian De Marco was critical of the church's stance.

"From March 31 we have a situation where the man entrusted with 14,400 of our kids is refusing to follow our child protection laws," Mr De Marco said.

Justice Dodds-Streeton said there was a risk the new laws could be challenged on constitutional or human rights grounds, however the cases were unlikely to succeed.

The failure to report laws are significantly different to those foreshadowed by Mr Ramsay last year.

Those laws were to be based on ones recommended by the Royal Commission into Institutional Responses to Child Sexual Abuse, which called for people who suspected child abuse was occurring within their institution but neglected to tell police to be prosecuted.

However the review concluded the laws should be widened to apply to all adults, because of the problems applying them solely to institutions.

Justice Dodds-Streeton said the royal commision's definition of the term "relevant institution" was too difficult to apply and open to legal "mischief".

For example, while some may count the Catholic church as one institution, the existence of different enclaves and auspices meant there was likely to be a "a fertile ground for legal and factual argument" about whether an abuser was a part of the same institution as the reporter, she said.

However stakeholders consulted through the process expressed concerns about how the broader laws would work in practice.

ACT Policing also said the offence would be difficult to enforce and prosecute, although considered that priests had a "duty" to report allegations regardless of where they came from.

The ACT Law Society and Legal Aid ACT expressed fears that the law could see adult victims prosecuted for failing to report their own abuser, although the bill will make it clear that cannot happen.

The Anglican Diocese was concerned the wider offence was open to "revenge reporting", although the legislation would make it a crime to file a false report, punishable by one year in jail or a $16,000 fine.

The Community Services Directorate was also afraid new reporting arrangements would aggravate over-reporting, particularly if they introduced a lower mental threshold than the mandatory reporting scheme.

To counter this, the bill will specify that an adult must reasonably believe abuse was occurring, rather than just suspecting.