The report, which covered 18 so-called Mother and Baby Homes where over decades young pregnant women were hidden from society, is the latest in a series of government-commissioned papers that have laid bare some of the Catholic Church's worst abuses.

About 9000 children died in all, the report handed down on Tuesday found - a mortality rate of 15 per cent. The proportion of children who died before their first birthday in one home, Bessborough, in County Cork, was as high as 75 per cent in 1943.

Infants were taken from mothers and sent overseas to be adopted. Children were vaccinated without consent.

Anonymous testimony from residents compared the institutions to prisons where they were verbally abused by nuns as "sinners" and "spawn of Satan". Women suffered through traumatic labours without any pain relief.

One recalled "women screaming, a woman who had lost her mind, and a room with small white coffins".

The head of the Irish Catholic Church unreservedly apologised to survivors and praised their determination to bring to light "a dark chapter in the life of church and society."

Relatives have alleged the babies were mistreated because they were born to unmarried mothers who, like their children, were seen as a stain on Ireland's image as a devout Catholic nation. The inquiry said those admitted included girls as young as 12.

Government records show the mortality rate for children at the homes where 56,000 women and girls, including victims of rape and incest, were sent to give birth, was often more than five times that of those born to married parents.

Prime Minister Micheal Martin will make a formal apology in parliament this week for what he described as "a dark, difficult and shameful chapter of very recent Irish history".

The government said it would provide financial compensation and advance long-promised laws to excavate some of the remains and grant residents, including many adoptees, greater access to personal information.

A coalition of survivors' groups said the report was "truly shocking" but it had mixed feelings because it did not fully account for the role the state played in running the homes.

The investigation was launched six years ago after evidence of an unmarked mass graveyard at Tuam was uncovered by amateur local historian Catherine Corless.

"I accept that the church was clearly part of that culture in which people were frequently stigmatised, judged and rejected," Archbishop of Armagh and all-Ireland primate Eamon Martin said in a statement.

"For that, and for the long-lasting hurt and emotional distress that has resulted, I unreservedly apologise to the survivors and to all those who are personally impacted by the realities it (the report) uncovers."

Australian Associated Press