Ireland could be in breach of international human rights conventions in not making any provision for de facto couples, according to new research for the Human Rights Commission.
Piecemeal provision may not be the best way to go, according to the report, and reform should be introduced through an overarching statute providing for relationship recognition.
Constitutional reform, providing for respect for private and family life beyond marital relationships, is desirable, it says.
The research, by Fergus Ryan and July Walsh, will be launched by the Minister for Justice today.
The commission wants to have the issues raised in the report addressed, according to its president, Dr Maurice Manning.
The report compares existing Irish legal provision for de facto couples (whether of the same or opposite sex) with the provisions in EU law and the protections in international human rights covenants.
It points out that the main provisions in EU law are in the areas of employment and freedom of movement, where there is limited equality of treatment.
Member-states are generally free to give married couples more favourable treatment than their unmarried counterparts.
However, the European Court of Justice tends to rely on the jurisprudence of the European Court of Human Rights in Strasbourg.
Article 8 of the European Convention on Human Rights, which protects a person's private and family life, has been found to extend to families other than those based on marriage. This court also treats suspiciously discrimination based on sexual orientation, according to the report.
It suggests that the failure to hold proceedings involving disputes between de facto couples in camera may infringe Article 8 of the convention.
The Irish courts' reluctance to uphold cohabitation contracts may also have to be revisited in the light of convention standards.
The provisions of the Pensions Acts, which reserve pension entitlements to surviving spouses, may involve indirect discrimination on the ground of sexual orientation.
The report argues that Ireland may also be in breach of the Belfast Agreement in its failure to introduce a civil partnership scheme for same-sex couples. The agreement provides for equivalent human rights protections between both jurisdictions, and since the introduction of the Civil Partnership Act in the UK there has been a divergence in these rights.