The head of the Royal Commission into Institutional Responses to Child Sexual Abuse, Justice Peter McClellan, disclosed in a speech on Saturday to a victims' group that he had personally written to the Vatican, seeking copies of all documents relating to complaints about abuse involving priests in Australia.

The Vatican has provided documents to the royal commission relating to two cases, but Justice McClellan wanted more information to find out how the church hierarchy in Australia, under the guidance or direction of the Vatican, responded to the allegations of abuse. In a written response, the Vatican said the Holy See maintained the confidentiality of internal church deliberations, adding that it would be inappropriate to provide such documents.

West Australian Liberal MP Steve Irons, who attended Justice McClellan's address at the 14th anniversary of the Care Leavers Australia Network (CLAN) at the Bankstown Sports Club in south-western Sydney, said he would ask the government to become involved.

A key figure in the national apology to the Forgotten Australians, Mr Irons also said he would take up the issue of funding being guaranteed to extend the work of the commission for another two years until 2017.

Justice McClellan used his address to defend the continuing work of the commission against commentary that was ''ill-informed'' on its practices and impacts.

This follows comments by Catholic lawyer Frank Brennan on Thursday that the commission was paralysing the agencies trying to deal with child sexual abuse.

Justice McClellan said the commission would present reports and recommendations when the detailed work needed for authoritative conclusions had been completed.

Leonie Sheedy, founder and chief executive of CLAN, a support group for victims of child sexual abuse, said the actions of the Holy See showed the Catholic Church was treating the Australian public with contempt.