Three priests and a former priest report the most senior Catholic clergyman in Britain, Cardinal Keith O'Brien, to the Vatican over allegations of inappropriate behaviour stretching back 30 years.
The Observer newspaper says they have demanded his immediate resignation.
The allegations come just days after Cardinal O'Brien called for Catholic priests to be able to marry and have children, saying some struggled with celibacy.
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.
As the most senior Roman Catholic in Britain he is the only person in Great Britain who will have a say in who succeeds Pope Benedict XVI when the pontiff stands down on 28 February.
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The pope was due to give his last blessing in the role in the Vatican today.
The accusations of inappropriate behaviour in the 1980s were made to the Pope's representative to Britain, Nuncio Antonio Mennini.
According to the Observer they 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 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 between took place between them.
The third complainant alleges "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.
Cardinal O'Brien has long big an outspoken opponent of gay marriage, so much so that Stonewall charity named him as "bigot of the year" in 2012.
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