Fathers have no rights in relation to their children because the law has not kept up with the modern Irish family, campaigners say.
Charity Families, Fathers and Friends have demanded an overhaul of legislation to make the registration of fathers' names on birth certificates compulsory.
The organisation has also called for fathers to be made automatic guardians of their children from birth, as part of its proposed charter for family law.
Sam Butt, lead counsellor with Families, Fathers and Friends, said the law needed to be changed to ensure protection for fathers and families.
"The stark reality is that fathers, married or unmarried, have no rights under the Constitution or in legislation," he said.
"Such rights can only be acquired through the consent of the mother or marriage to the mother of their children.
"Recognition of fathers' rights is not the only neglected aspect of family law.
"The system in itself is outdated, dysfunctional and fails in the services it was set up to provide."
The campaigners are also calling for fathers' rights to be enshrined in the Constitution and transparency of family court proceedings through a relaxation of privacy rules for hearings.
Equality minister Mary White said she was awaiting the publication of a Law Reform Commission report on the legal aspects of family relationships in the coming months and vowed to review legislation on guardianship, custody and access.