New revelations about the failure of the Catholic primate of all-Ireland to protect children from abuse have been uncovered by the BBC's This World show.
It found Cardinal Sean Brady had the names and addresses of those being abused by paedophile priest Brendan Smyth, but did not ensure their safety.
The investigation centres on a secret church inquiry in 1975 when a 14-year-old boy was questioned about abuse.
Smyth abused him and others in guesthouses on trips across Ireland.
In 1975, Cardinal Brady was a priest and teacher in County Cavan in the Republic of Ireland, when he was sent by his bishop to investigate a claim of child sexual abuse by a fellow priest.
That priest was later exposed as Ireland's most prolific paedophile, Father Brendan Smyth.
The first child to tell his parents about the abuse was 14-year-old Brendan Boland.
The man tasked with the secret church investigation that followed would later become the most senior priest in Ireland.
Sean Brady's role in the affair became clear in 2010, when it became known that he had been present when the abused boy was questioned.
He claimed, however, that the boy's father had accompanied him, and described his own role as that of a note-taker.
However, the BBC This World investigation has uncovered the notes Cardinal Brady took while the boy was questioned.
The child's father was not allowed in the room, and the child was immediately sworn to secrecy.
What Cardinal Brady failed to tell anyone in 2010 was that Brendan Boland had also given him and his colleagues the precise details of a group of children, some of whom, were being abused by Smyth.
Cardinal Brady did interview one of them and swore him to secrecy.
This World spoke to all of the children who Brendan Boland had identified; they all told the programme that to the best of their knowledge none of their parents or families were warned in any way about the paedophile Brendan Smyth.
Four of them had been abused by Smyth. Two of them continued to be abused after the 1975 inquiry.
One of them - originally from Belfast - told the programme that Smyth continued to abuse him for another year.
He also said Smyth abused his sister for a further seven years and then in turn, his four younger cousins, up to 1988.
Cardinal Brady did consider his position as Primate of all-Ireland when his role in the secret inquiry was first exposed.
The Catholic Church has said that "the sole purpose of the oath" signed by Brendan Boland in Cardinal Brady's presence was "to give greater force and integrity to the evidence given by Mr Boland against any counter claim by Fr Brendan Smyth".
The church also points out that in 1975, "no state or church guidelines for responding to allegations of child abuse existed in Ireland".
Irish Justice Minister Alan Shatter said the programme's revelations were "tragic and disturbing".
Abuse victims' campaigner Marie Collins, who was raped at the age of 13 by a hospital chaplain in Dublin, said Cardinal Brady should resign.
"I'm amazed no bishops have come out and said he should go," she said.
"We have priests and theologians being silenced by the Vatican - they can act against people whose views they feel are liberal, but they will not act against someone who not only endangered children but let them be abused.
"If Cardinal Brady came out and espoused the view that women should be ordained, he'd be gone within hours."
Gary O'Sullivan, editor of the Irish Catholic newspaper, said Cardinal Brady had questions to answer.
"If a child can see the need to save other children, how come priests, ministers of Christianity, cannot have the same awareness?" he said.
"If he wants to stay in this leadership position, he should show leadership and come out and answer these questions because this culture of silence failed children."
This World: The Shame of the Catholic Church was first broadcast on BBC One Northern Ireland on Tuesday. The programme is being shown on BBC Two at 21:00 BST on Wednesday.