The cardinal who until recently served as Britain's highest-ranking Catholic leader acknowledged unspecified sexual misbehaviour and promised to play "no further part" in the public life of the church.
The statement of Cardinal Keith O'Brien on Sunday came few days after his resignation from his position as archbishop of St Andrews and Edinburgh following a newspaper article that included unnamed priests' accounts of unspecified inappropriate behaviour.
O'Brien initially rejected the claims, saying he was resigning because he did not want to distract from the upcoming conclave which is due to pick a new pope.
But on Sunday, the Church of Scotland issued a statement quoting O'Brien as saying that there had been times "that my sexual conduct has fallen below the standards expected of me as a priest, archbishop and cardinal".
"To those I have offended, I apologise and ask forgiveness," the statement continued.
"To the Catholic church and people of Scotland, I also apologise. I will now spend the rest of my life in retirement. I will play no further part in the public life of the Catholic church in Scotland."
The admission was short on details. O'Brien gave no clue as to what exactly his sexual misbehaviour consisted of, but the confession comes as the Roman Catholic Church prepares to elect a successor to Benedict XVI, who resigned the papacy on Thursday.
O'Brien's time as cardinal ended as it began - in controversy. He got off to a rocky start when in 2003, as a condition of being made a cardinal, he was forced to issue a public pledge to defend church teaching on homosexuality, celibacy and contraception.
He was pressured to make the pledge after he had called for a "full and open discussion" on such matters.
At the time, O'Brien said he had been misunderstood and wanted to clarify his position. But statements made last week, before the scandal over his behaviour broke, suggested he never really changed his mind.
In an interview with the BBC, O'Brien said celibacy should be reconsidered because it's not based on doctrine but rather church tradition and "is not of divine origin".