Vatican Cardinal George Pell was interviewed Monday by an independent Australian committee investigating institutional child abuse cases by church clergy.
The cardinal, who was facing the Australian Royal Commission for the third time, was was too ill to return to Australia for questioning and testified via video link from the Hotel Quirinale in Rome.
Pell, 74, was questioned about his knowledge of paedophile activity by priests when he was a bishop and then archbishop in Melbourne from the 1960s to the 1990s.
Pell admitted child sex abuse has been an issue for centuries.
"The church has made enormous mistakes and is working to remedy those, but the church in many places, certainly in Australia, has mucked things up, has let people down," he told the commission.
"I am not here to defend the indefensible."
Pell said the problems in the church were not down to a "few bad apples" or the structure of the church.
"I think the faults overwhelmingly have been more personal faults, personal failures rather than structures," he said.
A number of complaints regarding clergy abuse of children were wrongly dismissed to protect the church, he said.
"Sometimes they were dismissed in absolutely scandalous circumstances," he said.
"At that stage, the instinct was more to protect the institution, the community of the church, from shame."
Pell is the third highest official in the Vatican and oversees the treasury department.
The commission is also expected to question Pell about allegations that he silenced a victim and ridiculed a complainant.
The inquiry has already heard about the impact of abuse on survivors, the knowledge local church leaders had of allegations of abuse, and the practice of moving offending priests from one parish to another.
A group of some 20 survivors from the Ballarat diocese, where the majority of the abuse took place, have travelled to attend the testimony in Rome.
They were seated across from the cardinal in the same room. He swore on a Bible that his evidence would be truthful as the query began.
The first half of the evidence was about his early years in priesthood, when he was working as a prIest in Ballarat, near Melbourne.
Pell criticized the former bishop of Ballarat, Ronald Mulkearns, who was investigated last week for his handling of a case involving paedophile priest Gerald Ridsdale, who was moved around to different parishes even after complaints of abuse emerged.
Pell said the destruction of incriminating documents by Mulkearns before a parliamentary investigation was "unacceptable."
Pell also said the way the church handled Ridsdale was a catastrophe for the victims and the institution.
"If effective action had been taken earlier, an enormous amount of suffering would have been avodied," he said.
The second half of the interview focussed on Christian Brothers, a community within the Catholic church that focuses on children's education in Ballarat. Some 280 members of the Brothers in Australia are accused of one or more complaints of child sexual abuse.
Pell's questioning is set to continue for at least three more days.
Trish Carter, a member of an abuse survivors support group, said the cardinal was evasive and avoided answering some important questions.
"He's a brilliant man and can remember a lot about his academic life, but he avoided answering anything specific," Carter, a member of the the Care Leavers Australia Network, told Australian Associated Press.
She said she wanted the top echelon of the church to take full responsibility for the abuse.
"It breaks my heart. I have really deep faith and I've taken a few risks by speaking out," she was quoted as saying.
"What's troubled me throughout the commission is the witnesses and perpetrators seem to have memory loss, yet the victims have vivid memories," said John Hennessy, another member.