CARDINAL Keith O'Brien has admitted that his sexual conduct fell "below the standards expected of a priest" in a move that has further rocked the Catholic Church.

The cardinal – until last week the most senior cleric in Britain – last night broke his silence on the allegations of "inappropriate behaviour" by asking for forgiveness for his actions and announcing that he would immediately withdraw from public life.

One leading Church commentator said the latest move is likely to leave Catholics in Scotland and the rest of the UK with a deep sense of betrayal.

The cardinal's admission came after a week of turmoil following claims of "inappropriate behaviour" from four men – one former and three serving priests.

Cardinal O'Brien, a long-standing and vociferous opponent of gay marriage, had announced his immediate retirement as Archbishop of St Andrews and Edinburgh last Monday.

In a brief statement last night, the 74-year-old cardinal said: "In recent days certain allegations which have been made against me have become public. 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.

"To those I have offended, I apologise and ask forgiveness. 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 Church in Scotland – and the rest of the world – has been left reeling by the allegations, more details of which emerged at the weekend.

They all date to encounters in the early 1980s between the future Cardinal O'Brien and the four other men when they were young priests or seminarians.

Cardinal O'Brien, who was born in Ballycastle, in County Antrim, and who had been the Archbishop of St Andrews and Edinburgh since 1985, resigned the day after the scandal first broke last Sunday. The Church claimed that the resignation was not directly related to the claims made against him by the four men.

The cardinal, who at the time also said he would not take part in the election for a successor to Pope Benedict XVI, had been due to retire later this month when he turned 75.

One accuser had claimed he was subject to unwanted attention from the cardinal when he was a 20-year-old seminarian at St Andrew's College, Drygrange.

Another priest said the cardinal called on him at his parish and that inappropriate contact took place, while a third priest claimed that he too had been subject to "unwanted behaviour" after some late-night drinking.

Although none of the men have been named in public, each of the cardinal's accusers has given a signed statement to the Vatican's ambassador to Britain, Archbishop Antonio Mennini.

Cardinal O'Brien's statement was greeted with a mixed response.

Historian Tom Devine, who had described the scandal as the biggest to hit the Catholic Church in Scotland since the Reformation, said the hypocrisy of the cardinal would leave a sense of betrayal.

He said: "The mood is likely to change radically to one of anger and a deep sense of betrayal. Christian charity demands we condemn the sin and not the sinner, but the hypocrisy which runs through this story leaves a bitter taste."

However, Liz Leydon, editor of the Scottish Catholic Observer, said: "The Scottish Catholic Observer would like to thank Cardinal Keith O'Brien for his leadership, and courageous action today in apologising and retiring from the public life of the Church in light of recent investigations into misconduct allegations. I once again offer my prayers and support to everyone affected by the situation and the news."

The Archbishop of Glasgow, Philip

Tartaglia, has been appointed by the Pope to govern the Catholic Archdiocese of St Andrews and Edinburgh until a permanent replacement is chosen.

John Haldane, Professor of Philosophy at St Andrews University and an authority on the Catholic Church, said: "This is going to be very shocking for ordinary Catholics. But if there's something to take comfort in it's the speed with which the whole matter has been dispensed.

"We are only one week down from the first story and now we have a statement which means that his life as an archbishop is effectively over.

"It is as complete a resignation as there can be and it is the right thing to do."

Colin MacFarlane, director of gay rights charity Stonewall Scotland, said: "We note with sadness that the cardinal didn't find it in him to apologise to gay people, their families and friends for the harm his vicious and cruel language caused."