All Australian churches should be made to open their books to account more thoroughly for their billions of dollars in assets and revenue, a member of the child abuse royal commission has said.

Robert Fitzgerald AM, one of the six commissioners who oversaw the five-year royal commission, will call on Wednesday for the scrapping of special exemptions that have until now allowed half of church charities, including much of the Catholic and Anglican church networks, to avoid financial reporting to the charities watchdog, the Australian Charities and Not-for-Profits Commission.

Commissioners Robert Fitzgerald, Justice Peter McClellan and Commissioner Helen Milroy at the Royal Commission into Institutional Responses to Child Sexual Abuse.

In an address celebrating the 10th anniversary of the not-for-profit law program of community legal group Justice Connect, Mr Fitzgerald will publicly declare for the first time that the arguments for the exemptions for "basic religious charities" do not hold up.

Mr Fitzgerald will explain how the exemptions had sent a "poor signal" to the wider community that some charities deserved special treatment simply because of their religious status.