There's plenty of bad language and abuse on social media, but it doesn't usually come from an elected representative in the Australian Parliament.

Libertarian senator David Leyonhjelm has labelled someone a "c---" on Twitter during an argument over Immigration Minister Peter Dutton's text mishap, in which he labelled a female journalist a "mad f---ing witch".

Senator Leyonhjelm, whose profile warns that "offensive abusers are blocked", dropped the "c-bomb" the day after he called another Twitter user a "witch".

He said Acting Opposition Leader Penny Wong, who had said she would find being called a witch offensive, "protests too much" and that "offence is chosen".

User @labourareliars then asked him "if someone called you a 'baldy lunatic f---wit', you'd be fine with it?"

"I'd call you a c---. And probably a rude name after that," Senator Leyonhjelm responded.

The Liberal Democrat senator is on a plane to Italy. A spokesman said the senator "is a rude man" but noted people offended by his use of the word have "probably used it themselves".

The outspoken senator is no stranger to causing controversy through language:

▪ In November, the NSW senator said that police had earned the saying "all cops are bastards".

▪ That same month, he called children "bundles of dribble and sputum" and praised people for not having them.

▪ In July, he labelled another Twitter user a "legitimate f---wit" when they raised his anti-wind farm views.

▪ In June 2014, he said he thought John Howard "deserved to be shot" when the former prime minister cracked down on firearms following the Port Arthur massacre.

▪ And following the 2014 Martin Place siege, he said tough gun laws had made Australia a "nation of victims".

Mr Dutton continues to face criticism for accidentally sending veteran News Corp political journalist Samantha Maiden a text message calling her a "mad f---ing witch". The message was intended for a colleague.

On Tuesday, Deputy Nationals leader Barnaby Joyce implored Australia not to become too "sterile" and politically correct.

"I like that Australia is to the point," he said.

"One of the great things about Australian politics is our informality and directness and I'd hate to lose that - even if there can be faux pas."

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