The Vatican's finance chief on Wednesday offered to testify at a child abuse inquiry in his home country of Australia, fending off accusations he had washed his hands of a problem that has plagued the Catholic clergy globally for decades.

Cardinal George Pell, the Vatican's prefect of the Secretariat for the Economy said he was "horrified" by claims of abuse and cover-ups by the Catholic church, and that he will give evidence if he is asked.

"I am horrified by the accounts that survivors have given in their evidence during the Ballarat hearings, and at the enormous impact the abuse has had on them, their families and the community," Pell said in a letter to the inquiry, referring to his home city where he served as an assistant priest from 1973 to 1983.

"I am also deeply saddened by the way the church authorities have failed in responding to these crimes. I am deeply to committed to assisting the royal commission and to doing anything I can to help survivors (including) giving evidence in person if asked to do so."

Pell was formerly Archbishop of Sydney, Australia's most senior Catholic.

His undertaking suggests he is switching to a more front-footed approach to a publicity nightmare that has been gathering around the church since Australia started a government-backed inquiry into institutional child abuse in 2013.

Victim groups have accused Pell of keeping the inquiry at an arm's length and putting the church's interests ahead of victims' interests by playing down its responsibility for individual crimes to avoid lawsuits.

Since the hearings began a week ago in Ballarat, witnesses have testified that Pell may have known about child abuse by a priest in the city 65 miles from the Victoria state capital of Melbourne, and that Pell offered one victim inducements to drop complaints.

Pell has repeatedly denied knowing about child abuse within the church, denied moving offending priests between parishes to avoid repercussions and denied taking measures to silence victims.

The inquiry published Pell's letter the same day as a former priest he once lived with, now imprisoned for molesting more than 50 children, told the inquiry that he understood he was committing crimes but never discussed his actions within the church because he did not want to lose his priesthood.