Thousands of institutions have been implicated in allegations of child sexual abuse, according to new data released by a royal commission.

As the Royal Commission into Institutional Responses to Child Sexual Abuse commences its final public hearing, chairman Justice Peter McClellan has urged child protection reform and proper redress for victims.

The $500 million inquiry is Australia's longest royal commission, starting in 2013 and due to finish with a final report to the federal government in December.

In his opening remarks to the hearing, Justice McClellan said governments and institutions needed to focus on redress and regulatory changes, "designed to ensure that so far as possible no child is abused in an institutional context in the future".