The Irish Premier has apologised on behalf of the Government to people affected by illegal adoptions.
Leo Varadkar said another "dark chapter" had been opened in the country's history after it was announced 126 births were illegally registered over a 23-year period.
Children and Youth Affairs minister Dr Katherine Zappone revealed on Tuesday that an independent review will be launched into the cases between 1946 and 1969, in which those affected may not know their parents were not their birth parents.
Mr Varadkar told the Dail on Wednesday: "This is potentially very traumatic for a lot of people and I am so sorry for it.
"I hope that we can deal with this, not just as a Government, but as politicians in a way that is really sensitive because it must be."
The Taoiseach said the people affected had a right to know their identity and their birth story.
He added: "What was done was wrong, what was done robbed children, our fellow citizens, of their identity.
"It was an historic wrong that we must face up to and again on behalf of the Government I'm very sorry for it."
The Taoiseach said the priority now was to contact all those people affected in a sensitive way.
"Nobody is going to get a knock on the door and suddenly have this information disclosed to their family," he said.
Earlier on Wednesday, Mr Varadkar recognised how difficult it will be for the families concerned.
"People are going to find out that they were adopted in this way having thought for the past 50-60 years that they were the natural child of the people who brought them up," he said.
"It's going to be really difficult for those parents who did bring up those people. They are going to have to have a very difficult conversation with the children they brought up."
Addressing those who criticised the Government's decision to release the information, Mr Varadkar said: "These are events that happened between 50 and 70 years ago and I know some people will say that what's in the past should be left in the past, and perhaps we shouldn't open this can of worms - but we have taken a different view as a Government.
"We have now very clear evidence that there were illegal registrations at the St Patrick's Guild, and we feel we have to share that information with the people who were affected."
Mr Varadkar said the next step was to go through the records of the other adoption societies.
He added: "We are opening what is another chapter from the very dark history in our country, but we are a different country now and I think the results from the referendum at the weekend show that."