A former priest regarded as one of the most notorious cleric child sex abusers of his generation, William Carney, has died in prison.

Fr Bill Carney, as he was known, was found dead in his cell on Saturday at the Midlands Prison, Portlaoise, Co Laois.

He had been extradited from the UK two years ago and was on remand awaiting trial in relation to 34 historical sexual assaults.

The Irish Times understands the 65-year-old was suffering from a cardiac condition and that foul play is not suspected.

The report of Commission of Investigation into the Catholic Archdiocese of Dublin, published in 2009, said he was one of the most serious sexual abusers it had reviewed.

He was based in the parish of Ayrfield in north Dublin for a period, having been appointed curate in the parish in 1977.

He was finally dismissed from the clerical state in 1992 almost a decade after complaints were first made that he sexually abused children.

The commission said there was evidence he acted in concert with other convicted clerical sex abusers, Fr Francis McCarthy and Fr Patrick McGuire, during the 1970s and 1980s.

The commission was aware of allegations of abuse in respect of 32 individuals, although there was evidence he abused many more.

Carney had access to numerous children in residential care and swimming classes. At one point, he inquired into the possibility of fostering children.

The first of many complaints were made by altar boys in 1983 whom he took swimming.

The commission says the mishandling of these complaints by the archdiocese was “nothing short of catastrophic” and displayed no concern for child welfare.

He pleaded guilty to two counts of indecent assault in 1983 and the archdiocese paid compensation to six of his victims.

However, he was in 1986 restored to priestly duties and continued to abuse children in Crumlin, south Dublin, where he was sent.

He settled in St Andrew’s, Scotland, where he married after being dismissed from the priesthood and also spent time in Spain and lived in England.

His marriage broke down and he was extradited to Ireland to face trial in 2013 in relation to 34 charges of sexual abuse on eight males and three females in Leinster between 1969 and 1989.