ONE-in-20 birth parents currently on a voluntary contact register has indicated a desire not to be reunited with their adopted son or daughter.
The statistics emerged as proposals were unveiled to put the register, operated by the Adoption Authority, on a statutory footing.
It is part of proposed new legislation that will allow people over 18 years of age who were adopted to have access to their birth certificate and other information.
Minister for Children James Reilly published the long-awaited General Scheme and Heads of the Adoption (Information and Tracing) Bill yesterday.
However, while it was broadly welcomed, many feel it is too restrictive.
Currently the register, which is run by the Adoption Authority, has 11,500 adopted adults and birth relatives on its books. One in 20 relatives has indicated they do not want to be contacted.
The most controversial aspect of the law will require those who were adopted to sign a statutory declaration before a Peace Commissioner or equivalent.
This is to say they will undertake to respect the privacy of their birth parent and not contact them before seeking assistance from Tusla - the Child and Family Agency.
Birth parents can indicate in the register that they do not want any contact at present.
Dr Reilly said the reason for the statutory declaration was to allow the proposed legislation to be legally sound.
"Once you sign a declaration you cannot use ignorance of the law as a defence, but this has not been a feature of contacts between children and their birth parents," he added.
However, Susan Lohan of the Adoption Rights Alliance said this measure would introduce statutory-based discrimination against adopted people.
"We cannot possibly endorse what we have seen of the proposals, as in some circumstances adopted people will be forced to sign away their rights in a way that further marginalises them on a statutory basis."
However, Paul Redmond of the Coalition of Mother And Baby Home Survivors, said it was "a breakthrough day at last and adoption secrecy has finally been rejected".
Dr Reilly said the heads of the Bill will go before the Joint Oireachtas Committee on Health and Children to allow all parties to give evidence before the legislation is drafted.
Children adopted after the law is in place will have an automatic right to their birth certificate and birth parents will be informed of the provision during the adoption process.
Children who were adopted from abroad will also be able to avail of the process.