DUBLIN — The Catholic Church in Ireland covered up widespread allegations of "evil" child sex abuse by priests for decades, according to a damning report released on Thursday.

Four archbishops routinely protected abusers and failed to inform police of the allegations, according to a three-year investigation into the Dublin Archdiocese, the country's largest.

Responding to the report -- the latest to reveal the scale of Catholic sex abuse -- the government immediately apologised for failing to protect children in Church care, and vowed in a statement that "this can never happen again".

"Whatever the historical and societal reasons for this, the government, on behalf of the state, apologises, without reservation or equivocation, for failures by the agencies of the state in dealing with this issue," it said.

The judicial probe discovered that the archbishops did not report abuse to police until the 1990s as part of a culture of secrecy and an over-riding wish to avoid damaging the reputation of the Church.

The report said: "All other considerations, including the welfare of children and justice for victims, were subordinated to these priorities."

It found that children who complained "were often met with denial, arrogance and cover-up and with incompetence and incomprehension in some cases. Suspicions were rarely acted on."

The study comes just six months after a landmark report in May horrified mainly Catholic Ireland by revealing widespread sexual, physical and emotional abuse of children in Catholic-run institutions dating back to the 1930s.

Irish Justice Minister Dermot Ahern (pictured above) said he read the findings with "a growing sense of revulsion and anger" and promised there would be "no hiding place" for the perpetrators.

"The report catalogues evil after evil committed in the name of what was perversely seen as the greater good," he said.

"There is no escaping the cruel irony that the church, partly motivated by a desire to avoid scandal, in fact created a scandal on an astonishing scale.

"In many, many cases the welfare of children counted for nothing and the abusers were left free to abuse, to visit evil on the innocent.

Victims welcomed the new report.

Marie Collins, who was abused as a child in 1960, said: "This is the end of a very long road for victims of abuse and particularly for those of us who spoke out for so many years, and who were vilified by the church (and) called liars".

The 750-page landmark report by judge Yvonne Murphy is damning in its criticism of failures to protect vulnerable children.

The probe examined complaints of abuse of over 320 children involving a representative sample of 46 priests in the Dublin Archdiocese between 1975 and 2004.

One priest admitted to sexually abusing over 100 children, while another accepted that he had abused on a fortnightly basis over 25 years.

It said the phrase, "don't ask, don't tell" was appropriate to describe the attitude of the archdiocese to clerical sex abuse for most of the period covered by the report.

"Typically, complainants were not told that other instances of child sexual abuse by their abuser had been proved or admitted," it added.

Responding to the report, human rights group Amnesty International called for an urgent referendum to enshrine children's rights in the Irish constitution to prevent future abuse.

"This report makes for deeply shocking reading, even after all that has gone before it," said executive director of Amnesty International Ireland Colm O'Gorman, who was himself a victim of the sexual abuse by priests.

"Bishops in Dublin colluded with child abusers, protecting them and hiding them, enabling them to prey on the innocent. Children were deliberately sacrificed to protect the Church," he said.