More than 35,000 children were placed in church-run institutions
An inquiry into abuse suffered by children in Catholic institutions in Ireland is "shocking reading" the country's parliament has been told.
About 35,000 children were placed in a network of reformatories, industrial schools and workhouses up to the 1980s.
More than 2,000 told the Commission to Inquire Into Child Abuse they suffered physical and sexual abuse while there.
The leader of Ireland's Labour Party said the report contains accounts of children being flogged.
Eamon Gilmore told the Irish Parliament that the report will shock many people when it is published.
The Irish Prime Minister Brian Cowen said: "We are all agreed that it is appalling the vista that will emerge in respect of a bygone day that is no longer with us, thankfully."
The BBC's Mark Simpson said the inquiry was expected to criticise the Church's handling of sex abuse complaints.
The institutions housed abandoned or neglected children, but courts also sent those guilty of truancy and petty crime.
Unmarried mothers were also sent to institutions known as Magdalene Laundries, many by their own families.
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Hundreds of the victims moved away from Ireland once they left the care homes and went to live in the UK.
Many of those who are alleged to have carried out the abuse are now dead
The commission was established in 2000 after the then Taoiseach Bertie Ahern issued an apology on behalf of the state to the victims of child abuse.
A government compensation scheme was also established. It has already paid out almost one billion euros in compensation and legal fees to 12,500 people.
Led by Mr Justice Sean Ryan, the commission's report is believed to be five volumes and 2,500 pages long.
Thousands of abused men and women testified to the commission, which was set up after a television series revealed the scale of the abuse.
Journalist Mary Raftery, who was behind the series, said the extent and depravity of the abuse was "profoundly shocking".
"It is off the scale in terms of anything we have any knowledge of or any ability to deal with, particularly, as it was perpetrated, in the main, by members of religious orders," she said.
"You'd be up at 6am and you had to go to two Masses," said Sadie O'Meara, a 15-year-old Tipperary girl working in Dublin.
"Your cell door was locked every night when you went in and you had a bucket and an iron bed and you couldn't look out the window. It was all bars.
"The food was absolutely brutal. And my mam died but they never told me she died. She died on Christmas Day but they never told me."
Ms O'Meara was speaking to Shane Harrison, BBC News in Dublin
Ms Raftery said the children ended up in "houses of horror" and were essentially locked up until they were 16.
"They emerged deeply disturbed and damaged and so many of them immediately emigrated," she said.
"They felt their country had abandoned them as well as everything else, as well as their religion, that just stripped them bare of any kind of support.
"It is an absolutely shameful episode in our history."
The allegations include sexual abuse and repeated beating of boys and girls with a leather strap.
Some punishments were said to be handed out for talking at mealtimes or writing left handed.
More than 100 institutions run by religious orders have been examined and the inquiry is expected to produce specific findings against a number of facilities.
Another major report is due next month on abuse by Catholic priests working in parish churches around Dublin.
The Archbishop of Dublin, the Most Reverend Diarmuid Martin, warned last month that it would "shock us all."