Britain' most senior Roman Catholic cleric has resigned following allegations he behaved in an "inappropriate" way with other priests.

Scottish Cardinal Keith O'Brien had been expected to take part in the conclave to elect a new pontiff that will start work after Pope Benedict XVI resigns on Feb. 28.

"For any good I have been able to do, I thank God. For any failures, I apologize to all whom I have offended," said O'Brien's statement, in which he made no reference to the recent allegations.

O'Brien said on Monday he had tendered his resignation to Pope Benedict some months ago as he was turning 75.

He said in his statement, "The Holy Father has now decided that my resignation will take effect today."

In another development on Monday, Benedict announced, "I leave the College of Cardinals the possibility to bring forward the start of the conclave once all cardinals are present, or push the beginning of the election back by a few days should there be serious reasons."

Traditionally the conclave begins between 15 and 20 days after the papal seat is vacated. That period included a customary nine-day period of mourning for a deceased pope.

Benedict is the first head of the Catholic Church in 600 years to resignl.

On Sunday it was announced that the Vatican was to investigate the allegations against O'Brien.

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

The Scottish Catholic Church says the cardinal, who is 74 and was due to retire in a few weeks, contests the claims and is taking legal advice.

O'Brien's statement followed newspaper reports that three priests and one ex-priest had complained about inappropriate behavior towards them in the 1980s.

In his statement O'Brien said he would not go to the Vatican to take part in the election for Pope Benedict's replacement.

"I do not wish media attention in Rome to be focused on me - but rather on Pope Benedict XVI and on his successor," he said.

O'Brien is Archbishop of Saint Andrews and Edinburgh, and Pope John Paul II proclaimed him a cardinal in October 2003.

The archbishop was born in Ballycastle, County Antrim, Northern Ireland, but came to Scotland as a young child while his father was serving in Britain's Royal Navy.

He studied at the University of Edinburgh where he gained a bachelor of science degree in chemistry and mathematics as well as a diploma in education.

In an interview with BBC Scotland on Friday O'Brien said he was open to the new pope coming from outside of Europe.

O'Brien said some issues such as abortion and euthanasia are "basic dogmatic beliefs" of "divine origin" which the Church could never accept.

But Cardinal O'Brien said it would be within the scope of the new pope to consider whether the Catholic Church should change its stance on other issues, which were not of divine origin.

"For example the celibacy of the clergy, whether priests should marry - Jesus didn't say that.

"There was a time when priests got married, and of course we know at the present time in some branches of the church - in some branches of the Catholic church - priests can get married, so that is obviously not of divine of origin and it could get discussed again."

The rule of celibacy is not a Catholic doctrine and could be changed by the next pope. There are some married priests in the church, such as those who have converted from Anglicism, not bound by the rules of celibacy.