The Emeritus Professor of Moral Theology at St Patrick's College seminary, Maynooth, Father Enda McDonagh, has said he favours the legalisation of same-sex unions.
In certain circumstances it would help ensure, to some extent, freedom from discrimination for a same-sex couple, and justice in dealing with one another, he said.
"Such acknowledgement in law and charity could liberate many gay couples to contribute more freely and fully to the common good of church and society. It would allow their joy in one another to spill over into the wider community," he continued.
Writing in the current issue of The Furrow magazine, he said that "by revealing the mystery of human sexuality in another form, it could play a redemptive, healing role in a society which in many ways is sexually sick".
Changes in the understanding and practice of homosexual relationships, as witnessed by many Christians,"suggest a more sophisticated analysis of how human embodiment may be expressed lovingly and sexually between same-sex partners, with no less stringent demands, of course, of fidelity and permanence than apply to heterosexual partners.
"In such situations it would be a mistake to use the term 'marriage', given its hallowed use in all traditions to describe that primary relationship of man and woman with its procreative potential," he said, but legal protection would be appropriate.
Referring to the recent Congregation for the Doctrine of the Faith document on the legalisation of same-sex unions, he said its "offensive language ... may not be excused on the grounds that it was simply repeating teaching by the same congregation, without, it may be said, having learned very much new about either courtesy or homosexuality in the meantime".
He continued that "of course discourtesy and offensive language are never the prerogative of one side in a heated dispute. Referring to Cardinal Ratzinger, head of the congregation, in terms of the Hitler Youth on a Morning Ireland programme, does not help the reasonable and loving debate needed," he said.
More disturbing was the congregation's "unwillingness or inability to distinguish between the legal protection of stable gay relationships and marriage as understood by most Christians and most civil jurisdictions", he said.