Allowing same-sex couples to marry would be the best way for the State to comply with its obligations in the area under European human rights law, a conference in Dublin was told at the weekend.
Prof Robert Wintemute of King's College London said legislators should consider "skipping intermediate structures" such as a registration scheme for same-sex unions in favour of full marriage rights, in order to avoid the possibility of new legislation being overturned in the European Court of Human Rights.
Only three out of the 46 countries bound by the European Convention on Human Rights (ECHR) had moved to grant same-sex couples marriage rights, but this situation was rapidly changing, he said.
A leading scholar in gender rights, Prof Wintemute said the best option for Ireland would be to allow three choices for all couples: civil marriage, an alternative registration system for couples who object to the term "marriage", and unregistered cohabitation.
Were Ireland to reject the extension of marriage rights to same-sex unions, the preferable option under human rights law would be to copy the Danish model of union registration, he said.
He was addressing a conference, hosted by the Irish Human Rights Commission (IHRC) and the Law Society of Ireland, on the ECHR and "human rights in committed relationships".
Prof William Binchy, a barrister and member of the IRHC, warned that the domino effect of European case law meant that "if we do nothing our law will undoubtedly be changed for us".
He said the recent Law Reform Commission report on the granting of improved rights to cohabiting couples contained "strains of old thinking".
The LRC report should be seen as "very much a first attempt" to tackle the issue. "We need a coherent attempt to address the question of partnership."
Options for legislators included the abolition of marriage, the introduction of a civil partnership, opening marriage to include heterosexual and same-sex unions, and introducing different categories of marriage.
On the latter, Prof Binchy said the introduction of divorce in 1995 had replaced a single definition of marriage by another single definition of marriage.
Speaking from the conference floor, Senator David Norris said legislation was badly needed in the area, especially in light of the recent Government decision to revoke social welfare benefits granted to same-sex couples by the Equality Tribunal.
The decision, taken in tandem with the "savage 16" cutbacks last year, meant Ireland had become "the only country in the past 10 years in the EU to remove rights and reintroduce discrimination against same-sex couples."
Meanwhile Mr Donncha O'Connell, lecturer in law at NUI Galway, told the conference that members of the Government needed to realise they were in a "committed relationship" with statutory bodies such as the Irish Human Rights Commission (IHRC) and the Equality Authority.
In a reference to recent comments made by Mr McDowell, Mr O'Connell said to dismiss the reasonably expressed collective view of the IHRC on the citizenship referendum as 'weak, tendentious and fanciful' might well be an impactful debating point.
But public discourse was not enriched by the kind of rhetoric that was intended to close and not open or broaden debate, he added.
Mr O'Connell said there was nothing undemocratic about robust debate being led by a statutory body, "especially when one remembers that it was the choice of elected representatives to create such bodies in both parts of the island of Ireland".
The conference heard that the incorporation of the ECHR into Irish law could have major implications for local authorities and other service providers in the State.
