The Dean of St Patrick's Cathedral, Dublin, Very Rev Robert MacCarthy, has turned down an invitation to a State reception honouring Cardinal Desmond Connell in Dublin Castle tonight.
The dean said last night he was doing so "on principle", and it was his practice to do so when he received invitations "in the name of the Taoiseach and Ms Larkin".
Accepting such invitations "encourages an idea that lesser relationships are on a par with marriage. I consider that there is also an urgent need for the State to support marriage, for good secular reasons, especially in relation to the rising numbers of single-parent families," he said.
Cardinal Connell will attend the reception, a spokesman confirmed, and many Catholic and Church of Ireland bishops are expected. But it is understood that other invited Catholic clergy will not attend because of the situation. About 1,400 invitations were issued by "The Taoiseach, Mr Bertie Ahern TD, and Ms Celia Larkin".
Ms Larkin, the Taoiseach's partner, was not in Rome when Dr Connell was elevated to the College of Cardinals.
A spokesman for Dr Connell said he was not aware of any discussion between the Taoiseach's office and Dr Connell before the invitations went out.
A Government spokesman said the invitations were issued in line with "normal procedure, since the Taoiseach took up office". Exceptions had been where Ms Larkin "would not be present, for whatever reason". She was "not available" to go to Rome, he said.
According to Catholic teaching, church members in second relationships may not receive Communion. The Taoiseach, who is living apart from his wife and who recently said he would not be seeking a divorce, is a regular communicant.
During the debate which followed the President, Mrs McAleese, taking Communion at a Church of Ireland service in 1997, Dr Connell refused to comment on the Taoiseach's position. Church sources said it is not its practice to comment on individuals, but on situations.
However, in an Irish Times interview in January 1998 the late Cardinal Basil Hume said he had written to the British Prime Minister, Mr Blair, to stop him receiving Holy Communion when he attended Mass with his wife Cherie, who is a Catholic.
Cardinal Hume said he explained to Mr Blair, a Church of England member, why he thought he should not receive Holy Communion in a Catholic church. Mr Blair no longer receives Communion at Mass. Cardinal Hume would not comment on Mrs McAleese taking Anglican Communion, but remarked, as reported, "that generally people in positions of leadership should give good example".