The Catholic Church's child protection watchdog has found that 53 allegations of child abuse against 44 members of three religious orders have resulted in no convictions.

The finding was made in audits by the National Board for Safeguarding Children in the Catholic Church (NBSCCC) of accusations against Sisters of Mercy, the Oblates and Legionaries of Christ.

The review focused on the handling of allegations since 1975, but some of the cases stretched back as far as 1941.

The Sisters of Mercy was criticised by the Ryan Commission for overuse of corporal punishment and neglect in residential institutions while "some very serious incidents of sexual abuse were perpetrated by lay staff in some schools".

Today's review found that since 1975, 31 allegations of child abuse have been made to the Sisters of Mercy against 17 nuns.

None of the 17 have been convicted of having committed an offence against a child or young person since 1975.

The Legion of Christ was mired in controversy when its late founder was condemned by Pope Benedict for sexually abusing seminarians among others.

Today's review found that four priests and brothers were subjects of allegations since 1975, all of which the order reported to police authorities and to the Republic's health and social services. 

There were no prosecutions in relation to the four priests and brothers in question.

The Oblate Fathers' main historical interface with children was in the former Daingean Reformatory School in Co Offaly where the Ryan Report found that staff sadistically flogged sexually abused boys.

Today's review found that between 1975 and this year, 13 Oblates were the subjects of allegations of child sexual abuse.

There were no prosecutions in relation to the 13 Oblates.

The NBSCCC said all of the reviews showed good safeguarding practice and prompt reporting of allegations to the civil authorities and good risk management.

The board's CEO, Teresa Devlin, said good habits have been created.

"What is most heartening here is that child safeguarding is an engrained component of the religious life and child-related activities of these orders and congregations. It has become a reflex and their first consideration," said Ms Devlin.