LONDON — Britain’s most senior Roman Catholic cleric has resigned amid allegations of inappropriate behavior made by priests.

The Vatican said Monday that Pope Benedict XVI had formally accepted the resignation of Cardinal Keith O’Brien, archbishop of St. Andrews and Edinburgh. The Observer newspaper reported Sunday that the Vatican had been notified of allegations of inappropriate behavior stretching back 30 years.

Three priests in Scotland, as well as a former priest, have lodged complaints to the Vatican's ambassador to Britain and demanded O'Brien's immediate resignation, according to the newspaper.

The 74-year-old cardinal has contested the claims and said he is taking legal advice.

O’Brien had been prepared to resign, citing his age as the cause. He turns 75 on March 17, and the Vatican said the pope had in November accepted a resignation letter under the condition of “nunc pro tunc,” meaning “now for later.”

The Vatican said Monday, however, that the pontiff had now accepted the resignation “definitively.”

Jeff J Mitchell / Getty Images, file

The Vatican confirmed Monday that it had accepted the resignation of Cardinal Keith O'Brien, 74.

It means O'Brien will not take part in the conclave to elect the pope's successor - a process that could begin earlier than March 15 after the rules governing the process were changed in a move announced Monday.

O’Brien said in a statement that it was the pope himself who had decided his resignation would take effect immediately.

“Approaching the age of 75 and at times in indifferent health, I tendered my resignation … some months ago,” he said. “The Holy Father has now decided that my resignation will take effect today.”

O'Brien would have been Britain's only elector in the papal conclave that will gather to decide on a successor to Benedict XVI.

"I will not join them for this conclave in person," O'Brien said. "I do not wish media attention in Rome to be focused on me -- but rather on Pope Benedict XVI and on his successor."

A hint of O’Brien’s accelerated resignation was found Sunday in Edinburgh, when the cardinal did not appear as scheduled to lead a Mass at St. Mary’s Cathedral. Instead, Bishop Stephen Robson made a statement on O’Brien’s behalf.

“A number of allegations of inappropriate behavior have been made against the cardinal,” the statement said. “The cardinal has sought legal advice, and it would be inappropriate to comment at this time. There will be further statements in due course.”

Robson is an auxiliary prelate in the Edinburgh diocese.

O'Brien's statement went on to say: "I have valued the opportunity of serving the people of Scotland and overseas in various ways since becoming a priest. Looking back over my years of ministry: For any good I have been able to do, I thank God. For any failures, I apologize to all whom I have offended."

Controversy
O’Brien had gained a reputation as a hard-line conservative and opponent of gay rights.

In 2009, O’Brien urged the Scottish National Party to abandon plans to give gay couples the same foster-parenting rights as straight ones, calling the idea “misguided” and saying that gays were known for unstable relationships.

Last year, he wrote an editorial in the Daily Telegraph in which he urged people to stand up against a proposal to allow gay marriage, which he said was “madness.” He referred then to same-sex marriage as a “grotesque subversion of a universally accepted human right.”

O’Brien’s stance and other comments led the gay rights group Stonewall UK last year to nominate him for its “Bigot of the Year” award.

“Ten-thousand people overwhelmingly, decisively voted that he should be given that award,” said Colin MacFarlane, director of Stonewall Scotland. “We don’t call people a bigot because they disagree with us. We reserve that for people who use the kind of language the cardinal has used. He has gone out of his way. It has not been fair discourse. His language has been cruel, hurtful and pernicious.”

The group's response to news of O'Brien's resignation was unsurprising.

“We trust there will now be a full investigation into the serious allegations made against Cardinal O’Brien,” MacFarlane said. “We hope his successor will show a little more Christian charity towards openly gay people than the cardinal did himself.”

Two weeks ago, the pope’s brother, the Rev. Georg Ratzinger, said scandals had troubled Benedict XVI and may have contributed to his decision to retire.

He specifically mentioned that Benedict had been bothered by the "Vatileaks" scandal in which a butler leaked secret documents, as well as the "the relationship to the Pius Brotherhood."

That organization, formally known as the Society of St. Pius X, fell into a harsh public spotlight in December when its leader, Bishop Bernard Fellay, said Jews were "the enemies of the church." His comment drew criticism from all corners of the church and from the public in general.

Georg Ratzinger said he thought his brother had handled those problems well but that they had taken their toll.

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This story was originally published on Mon Feb 25, 2013 6:55 AM EST