LONDON -- Cardinal Keith O'Brien, the first cardinal in history to recuse himself from a papal election over a personal scandal, has died, his archdiocese in Scotland said Monday. He was 80 and had suffered from a heart ailment.

O'Brien, once Britain's highest-ranking Catholic leader, resigned in disgrace as the archbishop of St. Andrews and Edinburgh in 2013 and recused himself from the conclave that elected Francis as pope after unidentified priests alleged in British newspaper reports that he acted inappropriately toward them.

The men said they had complained to church authorities about O'Brien's conduct but that the church had failed to respond. None of the men are believed to have been minors at the time of the purported misconduct.

After initially denying the allegations and impeding the investigation, O'Brien eventually admitted that his sexual conduct had "fallen below the standards expected" of a priest, archbishop and cardinal. He apologized and promised to play no further role in the public life of the Scottish church.

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"To those I have offended, I apologize and ask forgiveness. To the Catholic Church and people of Scotland, I also apologize," he said.

In 2015, Francis accepted O'Brien's resignation after he relinquished the rights and privileges of being a cardinal. He was allowed to retain the title, however. The decision was reached after O'Brien met with Francis, and after the Vatican sent its top sex crimes investigator to Scotland to look into the allegations against him.

A year earlier, Scottish church officials had reported that O'Brien had objected to a national church audit into how church officials had handled sex abuse cases in the Scottish church from 1952-2012. Without O'Brien's participation, the analysis never got off the ground.

O'Brien's official Vatican biography made no mention of the sex scandal, the Vatican investigation or the findings that he had impeded the 2012 sex abuse audit. After providing information about his education, ordination and honors, the brief biography said only that he didn't participate in the 2013 conclave, left Scotland for period of prayer, and resigned being a cardinal in 2015, without saying why.

Experts said his decision not to attend the 2013 papal conclave was unprecedented; never before had a cardinal stayed away from a conclave because of personal scandal, according to Vatican historian Ambrogio Piazzoni.

"In life, Cardinal O'Brien may have divided opinion - in death, however, I think all can be united in praying for the repose of his soul, for comfort for his grieving family and that support and solace be given to those whom he offended, hurt and let down. May he rest in peace," said Leo Cushley, Archbishop of St Andrews & Edinburgh.