The cardinal shocked the Roman Catholic community yesterday when he indicated that he would not contest claims against him and intended to retire permanently from the public life of the church.
The admission came a week after three priests and a former priest accused Britain’s most senior Catholic cleric of inappropriate behaviour dating back to the 1980s.
The cardinal, who stepped down from his post as Archbishop of St Andrews and Edinburgh in the wake of the scandal, has asked for forgiveness from those he had offended.
In a sweeping apology issued yesterday, he said of the claims: “Initially, their anonymous and non-specific nature led me to contest them.
“However, I wish to take this opportunity to admit that there have been times that my sexual conduct has fallen below the standards expected of me as a priest, archbishop and cardinal.”
The complaints have been reported to the Vatican, and a Scottish Catholic Media Office spokesman said: “We expect that they will be investigated and a conclusion drawn.”
The inquiry is not likely to begin until after a new pope is chosen. It is understood the cardinal, who will not attend the conclave, is currently out of the country.
The cardinal, who was born in Ballycastle, Co Antrim, had been the Archbishop of St Andrews and Edinburgh since 1985.
Ordained as a priest in 1965, he was proclaimed a cardinal by Pope John Paul II in October 2003. He was Britain’s most senior Catholic cleric.
One of Scotland’s most outspoken opponents of moves to legalise same-sex marriage, he was last year named “Bigot of the Year” by gay rights group Stonewall.
The claims against him were reported in the Observer newspaper last Sunday and the following day it was announced that the cardinal would quit his post with immediate effect.
His resignation was in fact accepted by the pope on February 18. The cardinal had been due to retire later this month when he turned 75 and the Scottish Catholic Media Office said his resignation had not been accelerated because of the allegations.
In fresh claims published yesterday, the former priest who reported Cardinal O’Brien over the allegations attacked the Church’s response to the complaints.
The man, who remains anonymous, told the Observer: “There have been two sensations for me this week. One is feeling the hot breath of the media on the back of my neck and the other is sensing the cold disapproval of the Church hierarchy for daring to break ranks. I feel like if they could crush me, they would.
“The vacuum the Church has created has allowed whimsy and speculation to distort the truth, and the only support I have been offered is a cursory email with a couple of telephone numbers of counsellors hundreds of miles away from me.”