Cardinal George Pell, the Holy See's Secretariat for the Economy, told an Australian royal commission into institutional responses to child abuse that the former Bishop of Ballarat Ronald Mulkearns never properly explained why Gerald Ridsdale was moved from parish to parish six times in the 1970s and 1980s.
Gerald Risdale committed more than 130 offences against 54 children while working as a chaplain St Alipius school in the city of Ballarat, Victoria state, between the 1960s and 1980s.
The Cardinal said of Bishop Mulkearn's actions: "I can't nominate another bishop whose actions are so grave and inexplicable.
"His repeated refusal to act is, I think, absolutely extraordinary."
From 1977 to 1984, Cardinal George Pell - who is not accused of abuse himself - was an adviser to Bishop Ronald Mulkearns.
He told the commission he never knew about Gerald Ridsdale's actions and that he took no responsibility whatsoever for the failing to report him to the police.
Mr Pell also said he had inquired about why Gerald Ridsdale was moved from parish to parish, however, he was never told it was because of his paedophilia.
Abuse survivors who've travelled to Rome to watch Cardinal Pell give evidence via video-link to the royal commission audibly gasped when he said of Ridsdale's abuse: "It's a sad story and it wasn't of much interest to me.
"The suffering of course was real and I regret that but I had no reason to turn my mind to the extent of the evils that Ridsdale had perpetrated."
Cardinal George Pell is expected to give evidence again until Wednesday or Thursday, and the royal commission continues.