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

Britain's most senior Roman Catholic cleric has been reported to the Vatican over claims of inappropriate behaviour going back 30 years, a newspaper says.

The Observer said three priests and one former priest have made the complaint against Cardinal Keith O'Brien, 74, leader of the Scottish Catholic Church.

They have demanded his immediate resignation, it said.

A statement from the Scottish Catholic Church said Cardinal O'Brien contested the claims and was taking legal advice.

Cardinal O'Brien stood down from some front-line duties in the Catholic Church in Scotland last year because of his age, and 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.

Late-night drinking

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 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."

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.

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

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 a new pope.

The chances of him not going, however, are "very remote", as not only has he denied the allegations but it is very difficult to prevent a cardinal from exercising their papal vote, unless he is detained by the state.

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 allegations made against Cardinal O'Brien.

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

"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."

Pope vote

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

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.

Last Friday, he said he had not yet decided who should be elected as Pope during the conclave, which is expected to be held next month.

The cardinal said he believed it might be time for a younger pontiff from part of the developing world, where the Catholic faith is thriving.

He also said he believed priests should be able to marry and have children if they wished to do so.

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.