The reception to honour Ireland's new cardinal Dr Desmond Connell is embroiled in more controversy over the inclusion of the Taoiseach Mr Ahern's partner Ms Celia Larkin on the official invitation.
Sources close to the cardinal claimhe is "distressed and embarrassed" by the decision to include Ms Larkin's name.
It was confirmed today the Very Rev Robert McCarthy, Dean of St Patrick's Cathedral, had turned down the invitation "on principle."
Figures in both churches have expressed disquiet in the past about Mr Ahern's relationship with his partner Ms Larkin, who regularly accompanies him to official functions at home at and abroad.
Dr McCarthy said it was his practice to turn down invitations received in the names of Mr Ahern and Ms Larkin because acceptance "encourages an idea that lesser relationships are on a par with marriage".
Cardinal O'Connell will be among more than 1,000 guests at the Dublin Castle reception.
But some Catholic clergy are understood to have turned down invitations.
A Government spokesman said the invitations had been issued in line with "normal procedure" since Mr Ahern took office four years ago.
PA