TEMPERS flared on Thursday's Liveline radio show when host Joe Duffy pulled the plug on a caller who labelled another woman a "homophobic feminazi".
The usually mild-mannered presenter exploded at the caller who levelled the slur against another guest, Laoise, during a discussion on the proposed rollout of unisex toilets in schools.
Laoise was arguing against the plans while the other caller came down in favour of them.
Laoise pointed out some of the potential complications with trans children using unisex toilets and used the term "trans identified boy" rather than "trans girl" in an example she gave to support her point.
The caller responded: "Seriously Joe, that's ridiculous. This woman has been given a platform and to be honest with you I think she's coming across, and this is just my personal opinion, she sounds like a homophobic feminazi."
The derogatory remark riled Duffy, who shouted: "Bye bye. No! None of that language on this programme. None of that language on this programme. Stop it."
The show went straight to an ad break following the comment and the caller was no longer on the line when the presenter and his guest resumed the discussion.
He said: "Laoise please accept my apology, I did not know that was coming.
"I thought that was an outrageous use of language. Nothing you have said on this programme so far would lead anyone to use those phrases so please accept my apology."
The Department of Education has issued new construction and refurbishment guidelines for schools, including an updated school design guide stipulating that most toilet facilities in future will be unisex, featuring self-contained cubicles with their own doors and communal access to sinks.
There are illustrations in the official design guide showing both boys and girls in the shared facilities.