Sydney talkback host Alan Jones breached commercial radio decency requirements by using a racist expression during an on-air discussion about politics.
During the Liberal Party leadership challenge last year, Jones suggested Finance Minister Mathias Corman needed to declare his loyalty.
"Anyone can stand... but they are mobilising to block Dutton," he said.
"The n----- in the woodpile here, if one can use that expression – and I'm not going to yield to people who tell us that certain words in the language are forbidden – the person who's playing hard to get is Mathias Cormann."
The phrase originated in the United States in the mid-19th Century and is thought to have referred to slaves who concealed themselves as they escaped to secure their freedom.
The turn-of-phrase used by the conservative presenter was widely reported in the media and attracted many negative comments on social media.
The Australian Communications and Media Authority said numerous complaints were made about the 2GB broadcast and the fact that it was not the first time Jones used the expression on air.
He used the phrase in 2013 to discuss Queensland state politics, in 2012 to criticise Malcolm Turnbull, in 2011 to describe cricket selectors, and in 2007 to describe the Commonwealth.
“The phrase used by Mr Jones has not been acceptable as part of everyday speech in Australia for some time and does not belong on our airwaves,” ACMA Chair Nerida O’Loughlin said.
The investigation did not find a breach of racial hatred codes but 2GB management agreed the phrase will not be used on-air again.
The ACMA also acknowledged that the station apologised within hours of the broadcast and that Jones issued an on-air apology the next day.
“When these things happen, all you can do is apologise,” he said.
“I have no difficulty doing that. I have never had any difficulty doing that. If you make a mistake, you have got to fess up. There is no-one else to blame but me.”