One of Pope Francis's closest advisers says Cardinal George Pell's position is "untenable".

Peter Saunders was hand-picked by the Pope six months ago to be the Catholic Church's commissioner for the protection of children.

Cardinal Pell has been under fire since allegations that he turned a blind eye to abuse resurfaced last week at the royal commission into child abuse in Ballarat.

"He is making a mockery of the Pope himself, but most of all of the victims and the survivors," Mr Saunders told the Nine Network's 60 Minutes program.

"More importantly, anybody who is a serious obstacle to the work of the commission and to the work of the Pope in trying to clean up the church's act over this matter needs to be taken aside very quickly and removed from any kind of position of influence."

Victims called on Cardinal Pell last week to front the royal commission following several claims he offered bribes or ignored warnings about Australia's worst pedophile priest, Gerald Ridsdale.

Cardinal Pell said he would co-operate with the investigations and would attend the hearings if he was asked to do so.