The Government has established an 18-month investigation into the Dublin archdiocese's handling of child abuse allegations.
The investigation commission, to be headed by Circuit Court judge Yvonne Murphy, will also investigate whether every other diocese is properly implementing safeguards ordered by the Ferns report.
However, Minister for Justice Michael McDowell said the Government is not planning a "Grand Inquisition" into the Catholic Church.
"The name of the game is not to uncover in minute detail every case of alleged sexual abuse right across Ireland," the Minister said.
The inquiry, which will cost €5.7 million, will investigate a representative sample of cases in the Dublin archdiocese dating between January 1st, 1975, and May 1st, 2004. It will examine the contacts between the church and State and local authorities once allegations had been made, or before they were made, and whether any efforts had been made to stop inquiries.
The Archbishop of Armagh, Dr Seán Brady, indicated in a letter this week to the Minister of State for Children, Brian Lenihan, that the church will co-operate with the investigation into his archdiocese, and the audit of other dioceses.
Mr Lenihan has asked the Health Service Executive to make sure that any allegations of child abuse are investigated collectively by church and lay authorities sitting on an inter-agency committee.
However, Mr Lenihan can refer any diocese to the new inquiry if evidence emerges that the Ferns recommendations are not being followed.
"It is very important that the HSE work is backed up by the inquiry. I have full power to notify certain things to the commission. That red flag provision is very valuable in backing up the work of the HSE in this area."
The performance of each and every diocese will eventually be "validated" by the inquiry to copperfasten public confidence, Mr Lenihan said.
Although the cases investigated in Dublin will be "a representative sample" of the total number of abuse allegations, Mr McDowell said: "It isn't a case of doing some sort of lottery on the blind."
The Government could have organised a Ferns-style inquiry into every diocese in the State, but this would have cost a fortune and taken years. "The process of inquiry must lead to some tangible outcome," Mr McDowell told journalists following the Cabinet's decision yesterday to approve the inquiry's proposed terms of reference.
"We have an emerging picture from Ferns and an emerging picture from Dublin of what the problem was about and what remedies were and were not put in place to address matters.
"These are very substantial exercises. They have to be conducted fairly. They can't be done in a slapdash way. We don't propose simply to unleash a Grand Inquisition right across Ireland into every allegation of child sexual abuse by every Catholic clergyman," he said.
"We have to, as a society, remember what these inquiries are supposed to do. They aren't simply fact-finding exercises. They are fact-finding with a view to changing how things are done to protect children...We are trying to find out how things can be done in the future and draw lessons from the past."
