A shocking and explosive report into child and sexual abuse in the Dublin Archdiocese today slammed the Catholic Church hierarchy for covering up the horrors.

Investigators revealed how Church and state authorities handled allegations of child abuse against nearly fifth priests. It found that the Church placed its own reputation above the protection of children in its care.

It also said that state authorities actually aided the cover-up by allowing the Church to operate outside the law.

Archbishop of Dublin Diarmuid Martin said "no words of apology would ever be sufficient" and offered "to each and every survivor, my apology, my sorrow and my shame for what happened to them".

He added that the "many good priests of the Archdiocese" shared his sense of shame.

The "Report of the Commission of Investigation into the Catholic Archdiocese of Dublin" covered a period from 1975 to 2004.

It exposed a culture of concealment where Church leaders prioritized the protection of their own institution above that of vulnerable children in their care.

The report said the avoidance of public outrage, which would inevitably follow high-profile prosecutions, appeared more important than preventing abusers from repeating their crimes.

Instead of reporting the allegations to civic authorities, those accused of horrific crimes were systematically shuffled from parish to parish where they could prey on new, unsuspecting victims.

The report stated: "The Dublin archdiocese's pre-occupations in dealing with cases of child sexual abuse, at least until the mid 1990s, were the maintenance of secrecy, the avoidance of scandal, the protection of the reputation of the Church, and the preservation of its assets."

It also said that the archdiocese "did its best to avoid any application of the law of the state".

It found that four archbishops — John Charles McQuaid who died in 1973, Dermot Ryan who died in 1984, Kevin McNamara who died in 1987, and retired Cardinal Desmond Connell — did not hand over information on abusers.

The report said that authorities in the Dublin archdiocese who were dealing with complaints of child sexual abuse "were all very well educated people".

It added that, considering many of them had qualifications in canon law, and in some cases civil law, their claims of ignorance were "very difficult to accept".

Civic authorities in Ireland, especially the police, were also criticised for their cosy relationship with the Church.

The report states that senior members of the force regarded priests as being outside their remit and it claims some police officers reported abuse complaints to Church authorities instead of carrying out their own investigation.

Irish police Commissioner Fachtna Murphy said it made for "difficult and disturbing reading, detailing as it does many instances of sexual abuse and failure on the part of both Church and State authorities to protect victims".

He added: "The commission has found that in some cases, because of acts or omissions, individuals who sought assistance did not always receive the level of response or protection which any citizen in trouble is entitled to expect from (the Irish police).

He said he was "deeply sorry" for the failures.

Irish Minister for Justice Dermot Ahern, whose department commissioned the report, called it a "scandal on an astonishing scale" where the "welfare of children counted for nothing".

He vowed to bring those who had carried out the abuse to justice, regardless of the amount of time which had passed.

Thursday's report comes six months after the publication of the Ryan Report in May, which heard evidence from 2,000 people who said they had suffered physical and sexual abuse while in the care of Catholic-run institutions.

The Ryan Report also found that Church leaders knew that sexual abuse was "endemic" in boys' institutions.