Sinn Féin President Mary Lou McDonald has called for the Irish Government to scrap proposed legislation that could see documents and records of mother and baby homes sealed for 30 years.
Mary Lou McDonald said the planned legislation will stop families accessing information about disappeared family members or babies buried in unmarked graves.
The Commission of Investigation (Mother and Baby Homes and Certain Related Matters) Records Bill 2020 is to be debated in the Seanad on Wednesday.
Campaigners have said the Bill will see documents collected by the Mother and Baby Homes Commission withheld from families.
The commission is examining the deaths of babies and children at several homes, including the Tuam home for mothers and babies, run from 1925 to 1961 by the Bon Secours Sisters.
"There are huge concerns over the lack of consultation regarding this Bill, and there are serious questions as to why (Children's) Minister (Roderic) O'Gorman is proceeding with this approach," Ms McDonald said during leaders' questions.
"Their main concern is the intention of the minister to transfer part of the Commission of Investigations archive to the child and family agency Tusla, without keeping a copy, as well as plans to seal the remainder of the archive for a period of 30 years.
"This will prevent people from accessing their records from the minister's archive and will stop families from accessing information about disappeared family members or babies buried in unmarked graves.
"It also means all the information that shows how abusive the system was will be withheld from the very people who are entitled to the truth.
"The role of the state and government should be to remove the veil of secrecy surrounding the mother and baby homes, not to reinforce it."
She said the Commission of Investigation Act enables the commission to deposit records with the Minister for Children following its dissolution.
Taoiseach Micheál Martin said the mother and baby homes represents a dark period in Ireland's history.
He denied claims that the legislation will put documents beyond the reach of families.
"The reason the legislation is being brought forward is to provide urgent and critical legal clarity surrounding the future use of the database compiled by the commission," he added.
"It's being brought forward to preserve invaluable information, not to put it beyond reach, as reported. That's not the intention.
"The Bill will make it possible for the database that is being compiled by the commission to be accessible under current legislation and to make it available for future information and tracing legislation.
"It is important to state that the purpose of this legislation is to preserve all of the records the commission has compiled through its work."
Ms McDonald said Ireland's mother and baby home scandal "casts a long and dark shadow" over the state's history.
"For decades these homes were shrouded in secrecy, and the awful abuse of single mothers and forced separation of families and the horrors of what happened in places like Tuam is still hard to comprehend," she told the Dail.
"Those who survived these institutions, those who didn't survive and their families are entitled to justice and entitled to truth.
"I am sure you received thousands of emails and letters from survivors regarding the fast-tracking through the Oireachtas this week of the Bill relating to their records."