A letter alleging sexual abuse by a priest in Chile has raised questions over what Pope Francis knew about the latest scandal marring the Catholic Church.

The Pontiff's trip to Chile last month was marred by controversy as he defended and embraced Bishop Juan Barros, who is accused of covering up abuse by disgraced priest Fernando Karadima in the 1980s and 1990s.

Karadima was convicted of child abuse by the Vatican in 2011.

During the trip, Francis said: "The day they bring me proof against Bishop Barros, then I will speak. There is not a single piece of proof against him. Everything is slander.

"You tell me that there are victims, but I did not see them."


Image: Bishop Juan Barros was promoted in Chile

But now the Associated Press has uncovered a letter on the alleged abuse that was sent to the Vatican in 2015.

Members of the pope's Commission for the Protection of Minors say that in April that year they sent a delegation to Rome specifically to hand-deliver a letter to the Pope about Bishop Barros.

The letter had been written by Juan Carlos Cruz, who said he suffered fondling and kissing at Karadima's hands, which he said Barros and others saw but did nothing to stop.

Marie Collins, an abuse survivor and former member of the Vatican's child protection panel, says she was among the ones taking the letter to the Vatican.

She says she and three other commission members handed the letter to the panel's chairman, Cardinal Sean O'Malley, who assured them it was passed on to the Pope.

"When we gave him (O'Malley) the letter for the Pope, he assured us he would give it to the pope and speak of the concerns," she told the AP.

"And at a later date, he assured us that that had been done."

Bishop Barros was appointed the head of the diocese of Osorno in Chile in the same year, despite the claims he knew of the abuse.

Catholic groups there have demanded that the bishop be removed from the diocese.

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Image: Pope Francis with the Chilean President Michelle Bachelet

Ms Collins, who quit the panel last year, said at least three of Karadima's victims have accused Bishop Barros of witnessing some acts, but he has denied knowledge of Karadima's actions.

After the trip, the Pope apologised to sexual abuse victims for his comments about Barros, acknowledging the word "proof" had hurt many people.

He said he was convinced of Barros's innocence following a Vatican investigation.