Image caption Cardinal O'Brien is the Archbishop of St Andrews and Edinburgh

Cardinal Keith O'Brien, Britain's most senior Roman Catholic cleric, has missed Sunday Mass after being accused of inappropriate behaviour.

Bishop Stephen Robson told St Mary's Cathedral in Edinburgh the Church "cannot not be saddened" by the news.

Three priests and one ex-priest have reportedly complained about the leader of the Scottish Catholic Church's behaviour some 30 years ago.

The Scottish Catholic Church said the cardinal, 74, contested the claims.

He is also taking legal advice, it added.

Cardinal O'Brien is due to retire next month when he turns 75.

He will have a say in who succeeds Pope Benedict XVI when the pontiff stands down on 28 February. He is Britain's only representative in the election for a successor.

Pope Benedict XVI has now given his final Sunday blessing at the Vatican before he steps down.

Pope informed

Cardinal O'Brien was due to celebrate Mass in St Mary's Cathedral to celebrate the eight years of Pope Benedict holding office.

Analysis The cases raised by Cardinal O'Brien's four accusers go back to the 1980s - so why are they being raised now just as he prepares to leave for Rome and the election for a new Pope? It seems that it wasn't a conclave that prompted the complaints initially - the letter complaining about Cardinal O'Brien was written to the Vatican ambassador, Archbishop Antonio Mennini, in the week before the Pope's unexpected resignation. It seems to have been timed instead for Cardinal O'Brien's planned retirement in the next few weeks. Two of the priests mentioned the "immense power" an active bishop has over his clergy, but with the Pope's resignation they have decided to publicise their allegations, evidently in an attempt to prevent Cardinal O'Brien taking part in the conclave. It's unlikely to work. Firstly any decision by Cardinal O'Brien to stay at home might be read as an admission of guilt, and secondly, Church law makes it very hard to prevent a cardinal who is qualified to vote from doing so.

But he did not appear and Bishop Robson, who is auxiliary bishop of the Archdiocese of St Andrews and Edinburgh, made a statement at the cathedral.

He said: "A number of allegations of inappropriate behaviour have been made against the cardinal.

"The cardinal has sought legal advice and it would be inappropriate to comment at this time. There will be further statements in due course.

"As always in times of need such as this we cannot not be saddened by the events of the last 24 hours.

"It is to the Lord that we turn to now in times of need."

A spokesman for the Vatican said "the Pope is informed about the problem and the question is now in his hands".

The Observer reported that the three priests and one former priest - from the diocese of St Andrews and Edinburgh - complained to the Pope's representative to Britain, nuncio Antonio Mennini, of what they claimed was the cardinal's inappropriate behaviour towards them in the 1980s.

The four complained in the week before 11 February, when Pope Benedict announced his resignation. The complainants have now called for the cardinal's immediate resignation.

The former priest claims Cardinal O'Brien made an inappropriate approach to him in 1980, after night prayers, when he was a seminarian at St Andrew's College, Drygrange, the Observer says.

The complainant, who is now married, says he resigned as a priest when Cardinal O'Brien was first made a bishop.

He reportedly says in his statement: "I knew then he would always have power over me. It was assumed I left the priesthood to get married. I did not. I left to preserve my integrity."

Media playback is unsupported on your device Media caption Cardinal Murphy-O'Connor says the church has become more transparent in dealing with allegations

A second statement from another complainant says he was living in a parish when he was visited by O'Brien, and inappropriate contact took place between them.

A third complainant alleges dealing with what he describes as "unwanted behaviour" by the cardinal in the 1980s after some late-night drinking.

And the fourth complainant claims the cardinal used night prayers as an excuse for inappropriate contact.

BBC religious affairs correspondent Robert Pigott says the allegations seem to have been publicised now because the four complainants do not want Cardinal O'Brien to go to the Vatican to participate in electing the new Pope.

There is only a "very remote" chance that he will not go, as not only has he denied the allegations but it is very difficult to prevent a cardinal from exercising his papal vote, unless he is detained by the state, our correspondent adds.

Petition protest

Cardinal Cormac Murphy-O'Connor, the former archbishop of Westminster, told the BBC's Andrew Marr Show he was "very sad" to hear of the claims made against Cardinal O'Brien.

"The cardinal has denied the allegations so we will just to have to see how that pans out," he said.

He added: "There have been other cases which have been a great scandal to the Church over these past years.

Cardinal Keith O'Brien Born on 17 March 1938 in Ballycastle, County Antrim, Northern Ireland

Ordained a priest on 3 April 1965

Obtained a bachelor of science degree in chemistry and mathematics from the University of Edinburgh and a diploma in education

Employed by Fife County Council as a teacher of mathematics and science from 1966 to 1971

Also served as assistant parish priest and as chaplain of St Columba Secondary School in Cowdenbeath

Spiritual director of St Andrew's College in Drygrange from 1978 to 1980

Rector of St Mary' College, Blairs, Aberdeen from 1980 to 1985

Ordained Archbishop of Saint Andrews and Edinburgh in 1985

President of the Bishops' Conference of Scotland March 2002 until 2012

Proclaimed Cardinal by John Paul II on 21 October 2003

Due to retire after he turns 75 on 17 March

"I think the Church has to face up - has faced up - to some of them very well indeed...

"I don't know what the Church will do. I think Cardinal O'Brien is very near to retirement and I suspect that his resignation, which is already with the Pope, because he's nearing 75 and every bishop has to retire - then presumably that will be accepted."

Cardinal O'Brien, who was born in Ballycastle, Co Antrim, has been the Archbishop of St Andrews and Edinburgh since 1985.

He has been an outspoken opponent of plans to legalise same-sex marriage and was named "bigot of the year" by gay rights charity Stonewall last November, prompting a storm of controversy.

Meanwhile, nearly 10,000 people in the United States have signed a petition calling on a senior Catholic clergyman to not participate in the election for the next Pope.

Cardinal Roger Mahony has been accused of helping priests suspected of sexual abuse to escape detection.

The Los Angeles archdiocese, of which he was formerly the head, has paid out millions of dollars in compensation to victims of child sex abuse.