Taoiseach (Irish PM) Micheál Martin has described revelations about illegal adoptions as "shocking".
He said "what happened was wrong" and "completely unacceptable".
RTÉ Investigates has reported that for decades thousands of babies born to unmarried mothers were illegally adopted.
Many only recently found out they were adopted, believing until then that the mother and father they grew up with were their natural parents.
Some also discovered they had been celebrating their birthday on the wrong date for decades, because their birth certificates had been falsified.
"I wasn't who I thought I was and I don't know who I am" is a constant refrain of those who were illegally adopted.
The programme features, amongst others, the case of Mary Dolan, a Belfast school teacher who was born in Dublin but placed with a couple in Northern Ireland who were registered as her parents on her birth certificate.
She later discovered that her birth mother had named her Rita and was told by social workers that she had a brother in the United States.
But DNA tests showed the two were not related.
"I was absolutely devastated," she says.
"To get an identity and then to have that literally ripped from you, it was gut-wrenching."
The programme also said that Professor Éamon De Valera Jr, a gynaecologist, and a son of the former Irish President and Taoiseach Éamon De Valera, facilitated illegal adoption long after it was made a criminal offence.
The documentary reports on one case where he arranged antenatal appointments for a woman who was not pregnant to give the impression that an infant she would later legally adopt was her biological child.
The issue of unmarried mothers and their babies has cast a long and dark shadow over Irish society.
Two months ago, the Irish state published a report on what happened in mother and baby homes for decades that led to Mr Martin apologising on behalf of the state to the residents.
Ahead of the broadcast of the programme, the taoiseach told the Dáil (lower house of parliament) that ministers were working on legislation that would give priority to the individuals who were illegally adopted and who are seeking information about their origins.