The royal commissioner looking at child sexual abuse has told a Melbourne audience that two-thirds of the perpetrators of sexual abuse in institutions were children or young people.

Justice Peter McClellan told a conference on child wellbeing that he was surprised to discover so many juveniles were involved in carrying out acts of sexual abuse in schools and religious institutions as has been revealed recent data.

"Surprisingly more than two-thirds of abusers in the institutional context were children and young people," he said.

The Royal Commission into Institutional Responses to Child Sexual Abuse started its work a year ago and has held 1,426 private sessions with complainants and has received 1,328 written submissions.

More than 1,000 people are still waiting to have private sessions.

But Justice McClellan says thousands of people who want to give evidence will not be heard.

He says more than 40 people a week come forward, but the commission does not have the resources to listen to all of them.

"Our current estimate suggests that if people coming to us continue at the present rate at the end of 2015, there may be 2,000 people who have asked for but not received a private session," he said.

Source: ABC