CATHOLIC clergy commit six times as much abuse as those in the rest of the churches combined, ''and that's a conservative figure'', a child protection expert says.

Patrick Parkinson, a Sydney University law professor, told the state inquiry into how the churches handle sex abuse yesterday that the figures for the Catholic Church were strikingly out of proportion.

He proposed a 12-month amnesty from charges of perverting the course of justice if the church opened all its files on offenders alive and dead, but said those involved in cover-ups would have to resign.

Earlier, Victoria Police Deputy Commissioner Graham Ashton set the inquiry's opening day alight with more broadsides against the Catholic Church's systemic obstruction of police inquiries over five decades.