Children's Minister Katherine Zappone described it as a "very serious and sensitive issue"
Dozens of people placed for adoption in St Patrick’s Guild may not know they are adopted.
The child and family agency Tusla has identified 126 cases where births were incorrectly registered by the former agency between 1946 and 1969.
They are cases where the adoptive parents of the child were recorded as the birth parents without an adoption order.
79 of the people affected may have no idea they were adopted and "may be entirely unaware of the true circumstances of their birth".
An independent review has been ordered into the incorrect registration at St Patrick’s Guild.
Children's Minister Katherine Zappone says while the practice of incorrect registrations has been known about for many years, it has been 'extremely difficult' to prove and identify individual cases due to the "deliberate failure of those involved to keep records".
Minister Zappone explained: “This is a very serious and sensitive issue. People have the right to know of their true origins and, where we have clear evidence, I believe we have an obligation to tell the people affected.
"Some may know already, but for others it will be entirely new and very difficult information indeed. Tusla has developed a plan for making contact with people and for providing the right supports for them as they absorb this information."
In a separate statement, Tusla confirmed it had identified at least 126 cases of incorrect registrations in the St Patrick's Guild records - saying "significant work remains to identify, locate and inform those affected".
The agency said: "At this point in time, we cannot say with certainty how long this process will take. Tracing people is often slow, labour-intensive work, but we have created an experienced social work team dedicated to tracing these people in the hope that the work will be completed as quickly as possible.
"This is an extremely sensitive issue and one which we acknowledge may cause upset and anxiety for those affected, as well as adopted people, adoptive parents and birth parents across the country. Tusla will ensure that those affected will be treated with dignity, respect, sensitivity and a true sense of compassion."
Following the discovery, further investigations will be carried out to see if there is any evidence of incorrect registration in the records of other former adoption agencies.
As there are around 150,000 records, Minister Zappone says a 'targeted sampling exercise' will be conducted first to see if a major trawl is necessary.
Anyone looking for information about the new information can contact a Tusla Freephone helpline, which is operating at 1800-805-665 between 10am and 4pm on weekdays.
St Patrick's Guild Adoption Society was established in 1910 by the Sisters of Charity, and ceased operations in 2014.
Tusla has stressed that the only people potentially affected were born between 1946 and 1969.
Additional reporting by Stephen McNeice