The head of the royal commission into child sex abuse has condemned Catholic leaders for failing to recognise the sexual assault of children as a crime.

Justice Peter McClellan has spoken about the royal commission for the first time in a speech to the Australian Human Rights Commission.

Justice McClellan reflected on the fact many leaders of the Catholic Church argued sexual abuse was a "moral failure" rather than a criminal act.

"I cannot comprehend how any person, much less one with qualifications in theology ... could consider the rape of a child to be a moral failure but not a crime," he said.

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"This statement by leaders of the Catholic Church marks out the corruption within the church both within Australia, and it seems from reports, in many other parts of the world."

Justice McClellan also said he was disheartened by delays in institutions signing up to the national redress scheme for survivors of child abuse.

"I hope this is not because of a desire to put the protection of the institution's assets ahead of the needs of survivors," he said.

If you or someone you know is impacted by sexual assault, domestic or family violence, call 1800RESPECT on 1800 737 732 or visit 1800respect.org.au. In an emergency, call 000.

Readers seeking support can contact Lifeline crisis support on 13 11 14, Suicide Call Back Service on 1300 659 467 and Kids Helpline on 1800 55 1800 (for young people aged 5 to 25). More information is available at Beyond Blue.org.au and lifeline.org.au.