Fianna Fáil leader Micheál Martin has said it was unchristian for a priest to refuse communion to his Transport spokesman Robert Troy.
It was reported last weekend that Mr Troy was refused communion at a local funeral due to his position on abortion.
Mr Troy sided with his leader in the face of deep opposition within his party and voted Yes in last year’s referendum to repeal the Eighth Amendment.
Mr Martin's decision to back the proposal to liberalise the country's abortion laws was a major turning point in the run-up to the campaign, but a majority of his TDs defied him and opposed the referendum.
He revealed his change of stance in a Hot Press magazine interview, having previously described himself as pro-life.
Mr Martin said it went “against the grain” of Christianity to deny Mr Troy communion.
“I think it was unacceptable and I was surprised,” he said.
“It was unchristian, it was very unchristian thing to do. It goes against... the grain in terms of the true meaning of Christianity.”