Gay and lesbian couples should be able to register their relations with the State, but not marry, according to one of the options put forward by an expert group to the Government.
Such couples, and those involving a man and a woman, would be able jointly to register all of their assets, including a home, in a contract that would subsequently be recognised by the courts.
The introduction of full gay marriage is both "unnecessary and vulnerable to constitutional challenge", according to the group chaired by former Progressive Democrat TD Anne Colley.
However, the introduction of full civil partnership for gay and lesbian couples would not "suffer from the same constitutional vulnerability as full civil partnership for opposite-sex couples".
Gay and lesbian couples should be able to apply to adopt a child - but only if they are covered by nothing less than full civil partnership, the 90-page report published last night made clear.
A limited civil registration scheme could apply to opposite-sex and same-sex couples, and would come into force three years after they had lived together, or immediately on the birth of a child, the Working Group on Domestic Partnership said.
"Under a presumptive scheme, couples living together for a specified period would automatically acquire rights and responsibilities towards each other unless they can prove an intention to exclude themselves from such a scheme," the report reads.
Bereaved partners who are not married are often badly affected by the wills left by the deceased, it said: "Without a joint ownership agreement or a valid will, the non-owning co-habiting partner may have no legal claim on a pro-perty on the death of the owning partner regardless of the period of time they resided in the pro-perty together," it said.
Examining civil marriage for same-sex couples, the working group acknowledged that it would achieve "equality of status" for gay and lesbian couples, offer "certainty and predictability" and be "administratively straightforward".
However, it continued: "Introducing civil marriage for same-sex couples is likely to be vulnerable to constitutional challenge given the special position it is afforded in the Constitution and the interpretation of the definition of marriage in constitutional actions before the courts that marriage is the voluntary and permanent union of one man and one woman."
Full civil partnership, along the lines of that introduced in Northern Ireland, would "address the majority of the issues encountered by same-sex couples".
Opposite-sex or same-sex couples who have signed up to a limited civil registration scheme should not be allowed to adopt as a couple, though it would be possible for one of the partners involved to apply on their own.
Same-sex couples who are civilly married should, however, be allowed to apply to adopt, especially in cases where a child has been conceived by one of the partners in another relationship, or where a child has been born through assisted reproduction.
A bereaved gay or lesbian partner should be able to go to the courts to argue that the deceased had not made proper provision for him or her, it also said.
There were 77,600 co-habiting couples recorded in the 2002 census, up from 46,300 in the 1996 census. The number of declared same-sex couples rose in the same period from 150 to 1,300, although this is believed to be a considerable underestimation.