The Limerick-based Augustinian priest wrote in the Irish Times that he will vote on the grounds of “respect for the freedom of others who differ from us.”
He went on to recall the gospel passage where Jesus “tells us to give to Caesar what is Caesar’s and to God what is God’s.”
O’Donovan wrote, “we are giving to Caesar what is Caesar’s. In a democracy, Caesar is the people.”
The vocal priest said churches “have views, ideals and laws about the family, and they quite properly teach their members about those views… But when we become legislators, as we do when we vote in referendums, we legislate as citizens for all our fellow citizens.”
He continued, “It is possible to have deep and passionately-held convictions without seeking to have those convictions imposed by the state on fellow citizens who do not share them.”
And concluded saying, “respect for the freedom of others who differ from us is part and parcel of the faith we profess. For these and for other reasons I will be voting Yes.”
Father Iggy’s comments come the day after Bishop of Elphin, Kevin Doran, told Ireland's NewsTalk radio that gay couples with children “are not parents.” The Bishop said he believes “the jury’s out” on whether people are born gay.
When he was asked where he believed homosexuality comes from – whether it was what God intended – he said, "That would be to suggest that if some people who are born with Down syndrome or Spina Bifida, that that was what God intended either."
The Bishop, Dr Doran, also spoke about how it was wrong for women who had been raped to use abortions as a way to “get back” at their attacker.
Doran also mentioned during his interview that he himself had been confused about his sexuality during his teenage years.
In response Father Iggy said, “I would be very slow to bring a crowd onto a field where we ourselves are vulnerable.
"In view of our recent history, our [the Church's] street credibility in these areas is not very high – so it is an area we need to be extra-sensitive around and Bishop Doran must know that."
He also referred to case of disgraced Scottish prelate Cardinal Keith O'Brien who was vehemently anti-gay. O’Brien was found to have molested seminarians.
"As we learn more, it would be more unforgivable for us to get it wrong," he warned.
Fr Brendan Hoban, of the Association of Catholic Priests, asked recently whether “the bishops, Iona [Institute] and the hardline fundamentalists [had] any idea of the damage they’re doing to the church” with their stance on the upcoming referendum.
“A positive result for ‘Catholic’ forces [a No vote in the referendum] could do huge damage to the Irish Catholic Church.
“Can someone in authority not say that Catholics follow their own teaching but that legislators have to legislate?”
Meanwhile the video below of grandparents Brighid and Paddy has gone viral in Ireland. It was released by the Vote With Us campaign, which has created an archive of videos of ordinary voters and well-known public figures.
In their video these grandparents highlight why they will vote Yes on May 22: