Three priests and one former priest have sent statements to the papal nuncio, Antonio Mennini, alleging impropriety dating back to 1980.
As head of the Roman Catholic Church in Scotland, next week O'Brien will be part of the conclave choosing the next Pope, but now he faces demands for his immediate resignation.
As reported by The Observer, one of the priests alleges that he has needed counselling after an inappropriate relationship with O'Brien.
A second complainant said that he was 18-years-old when O'Brien made an inappropriate approach after night prayers.
A third said he was invited to 'get to know' O'Brien at the archbishop's residence only to face 'unwanted behaviour' from O'Brien after late-night drinking.
The four are all from the diocese of St Andrews and Edinburgh.
A spokesman for the cardinal said that he contests the allegations.











