A new law will make it a crime for any adult in Canberra not to report suspected child sexual abuse.

Key points: The obligation to report sits alongside existing mandatory reporting schemes

The obligation to report sits alongside existing mandatory reporting schemes Under the new laws an adult must have reasonable grounds to believe a child has been abused

Under the new laws an adult must have reasonable grounds to believe a child has been abused Adults who fail to report child sexual abuse could face prison

ACT Attorney-General Gordon Ramsay said the offence — with a penalty of up to two years in prison — would apply to all Canberrans, because child abuse did not only occur within institutions.

"We have a responsibility, the whole of the community has a responsibility, to make sure our children are safe," Mr Ramsay said.

The obligation to report would be simpler than mandatory reporting schemes that previously covered professions like teachers and health staff.

Under the new laws if an adult believed, on reasonable grounds, that a child had suffered sexual abuse it would become criminal not to report that to police.

On Thursday Mr Ramsay will introduce legislation to create the new offence, which will also extend to the Catholic Church's confession booth.

But the Government's own report into the issue recommended including confessionals would have little impact on detecting or prosecuting child sexual abuse.

The new crime appears to put clergy into an impossible position: report child abuse and be immediately excommunicated under canon law, or not report abuse and be imprisoned under Australian law.

Abusers will 'probably avoid confession altogether'

Justice Julie Dodd-Streeton's report suggested the new offence would turn up very few cases from the confession booth.

"In our opinion, the imposition of an obligation to report child sexual abuse ... is unlikely to result in many detections of, or successful prosecutions for, either child sexual abuse or breaches of the reporting obligation itself," Ms Dodds-Streeton wrote.

"Where sexual abusers of children are Roman Catholics who would otherwise attend confession, they will probably avoid confession altogether."

But Mr Ramsay said the evidence was clear that breaching the confessional would reduce child abuse.

"The Royal Commission was very clear … on a number of occasions an offender committed an act, and then went to confession and felt a sense of absolution, and then went and reoffended," he said.

"The seal of the confessional has played a part in children being further abused."

Theologian and former Catholic priest Paul Collins said that the new law would dissuade child sex offenders from disclosing to clergy who could monitor their behaviour.

"Catholics have not been going to confession for the last 30 years, I haven't been to confession and I'm a practicing Catholic, there's a confession for you," Mr Collins said.

"That's true of the vast majority of Catholics and any person who has committed the crime of paedophilia.

"It's most unlikely that they're going to go confession if they know that the priest is going to legally have to report them."

Mr Ramsay said the Government set the laws on how a society operated, and that included the church.

"There are sensitivities, there are emotions impacting on the practice of faith, but no practice of faith should ever put a child at risk," he said.

The ACT Government has the support needed to pass the laws, which would come into effect later this year.