Photo: The Canadian Press

Members of the movement Laicos de Osorno sing while holding up images showing the Rev. Fernando Karadima, and his protege Juan Barros, bishop of Osorno, with a message that reads in Spanish: "A bishop who covers up cannot be a priest," during a vigil in front of the Cathedral of Santiago, Chile.

Pope Francis' top adviser on clerical sex abuse implicitly rebuked the pontiff over his accusations of slander against Chilean abuse victims, saying Saturday that his words were "a source of great pain for survivors of sexual abuse."

Cardinal Sean O'Malley, the archbishop of Boston, said he couldn't explain why Francis "chose the particular words he used" and that such expressions had the effect of abandoning victims and relegating them to "discredited exile."

In an extraordinary effort at damage control, O'Malley insisted in a statement that Francis "fully recognizes the egregious failures of the church and its clergy who abused children and the devastating impact those crimes have had on survivors and their loved ones."

Francis set off a national uproar upon leaving Chile on Thursday when he accused victims of the country's most notorious pedophile priest of having slandered another bishop, Juan Barros. The victims say Barros knew of the abuse by the Rev. Fernando Karadima but did nothing to stop it — a charge Barros denies.

"The day they bring me proof against Bishop Barros, I'll speak," Francis told Chilean journalists in the northern city of Iquique. "There is not one shred of proof against him. It's all calumny. Is that clear?"

The remarks shocked Chileans, drew immediate rebuke from victims and their advocates and once again raised the question of whether the 81-year-old Argentine Jesuit "gets it" about sex abuse.

The Karadima scandal has devastated the credibility of the Roman Catholic Church in Chile, and Francis' comments will likely haunt it for the foreseeable future.

O'Malley's carefully worded critique was remarkable since it is rare for a cardinal to publicly rebuke the pope in such terms. But Francis' remarks were so potentially toxic to the Vatican's years-long effort to turn the tide on decades of clerical sex abuse and coverup that he clearly felt he had to respond.

O'Malley headed Francis' much-touted committee for the protection of minors until it lapsed last month after its initial three-year mandate expired. Francis has not named new members, and the committee's future remains unclear.

"It is understandable that Pope Francis' statements ... were a source of great pain for survivors of sexual abuse by clergy or any other perpetrator," O'Malley said in the statement. "Words that convey the message 'if you cannot prove your claims then you will not be believed' abandon those who have suffered reprehensible criminal violations of their human dignity and relegate survivors to discredited exile."

Francis' comments were all the more problematic because Karadima's victims were deemed so credible by the Vatican that it sentenced him to a lifetime of "penance and prayer" in 2011. A Chilean judge also found the victims to be credible, saying that while she had to drop criminal charges against Karadima because too much time had passed, proof of his crimes wasn't lacking.

Those same victims accused Barros of witnessing the abuse. Yet Francis said he considered their accusations "all calumny" and that he wouldn't believe them without proof.

Catholic officials for years sought to discredit victims of abuse by accusing them of slandering and attacking the church with their claims. But many in the church and the Vatican have come to reluctantly acknowledge that victims usually told the truth and that the church had wrongly sought to protect its own by demonizing and discrediting the most vulnerable of its flock.

O'Malley said he couldn't fully address the Barros case because he didn't know the details and wasn't involved. But he insisted the pope "gets it" and is committed to "zero tolerance" for abuse.