The Vatican has refused to hand over the files of Australian priests accused of sex crimes to the child abuse royal commission.

The Vatican said the commission's request for documents on each allegation involving an Australian cleric was "neither possible nor appropriate".

Cardinal George Pell.

Reasons included ongoing church investigations, and that internal working documents were the sovereign property of the Holy See.

Cardinal George Pell, now working in Rome, was asked if he sought an assurance from the Vatican that any document the royal commission needed would be provided.