RTE has confirmed it is investigating an incident in which one of its freelance producers labelled Irish journalist David Quinn "a poisonous c**t" on his Twitter page.
Pat O'Mahony, who works on radio documentaries and the Ireland's Biggest Hits show for RTE told the Sunday Independent he posted the tweet after losing his temper while listening to Mr Quinn on the Today with Pat Kenny show on RTE radio.
Mr O'Mahony said: "I am the first to say to people if you don't want something to end up on a poster outside your mother's house or on a billboard, then don't post it on Twitter.
"But on this particular day I was working from home when I heard him accuse the Labour party of being a pro-abortion party. And I lost my temper with him, [which is] never a good thing to do. The moment I hit the send button I knew it could come back to bite me.
"I will apologise to him. It was childish and unnecessary, whatever I think of his politics."
He added: "My worry now is that RTE will get dropped into it. I want to make it clear that I am a freelancer who works for many different companies, RTE being just one of them."
Mr Quinn, who is a columnist for the Irish Independent and director of the Iona Institute, described the tweet as "shocking and unprofessional".
"The abuse on Twitter has gotten particularly hot and heavy following the Savita case. But what made this so unusual was that Mr O'Mahony does a lot of work for RTE. That made it incredibly unprofessional. I was appalled – it was the worst type of abuse in terms of the language used.
"There seems to be an enormous intolerance for anyone who has an unfashionable opinion these days," he said.
A spokesperson for RTE said: "Mr O'Mahony is a freelance producer. RTE is looking into the matter. RTE totally disassociates itself from these remarks. There is no further comment at this time."