Queensland Nationals MP George Christensen used an appearance on a US conspiracy theorist's online show to advocate for protests outside Australian consulates over the country's COVID-19 restrictions.

At one point during the InfoWars interview, Mr Christensen laughed when host Alex Jones compared Australia's quarantine facilities to the Auschwitz concentration camp.

"I denounce the comments in the strongest possible terms," Mr Morrison said in a statement on Tuesday.

"The Holocaust was an evil abomination. Respect for the victims requires that it never be referenced in such a trivial and insensitive manner."

Nationals leader and Deputy Prime Minister Barnaby Joyce tweeted from London that he had been made aware of the latest comments by Mr Christensen.

"Accordingly, I have contacted him twice in the night to affirm that any parallel of domestic policy with the abomination which was the holocaust requires an immediate rebuke.

"I have asked Mr Christensen to be far more aware of any platform he speaks on and to ask himself of the history of those platforms and if participation on it is wise," Mr Joyce wrote.

The InfoWars program has been banned on Facebook and YouTube for hate speech violations and has made multiple false claims about the pandemic.

Labor senator Katy Gallagher said Mr Christensen's comments could lead to Australian diplomats in consulates being targeted.

"Encouraging protest action or inciting violence at Australian embassies overseas, where we have public servants working in the national interest ... is a particularly dangerous comment," she told reporters in Canberra.

"He finds that funny, (but) this is a line that has been crossed."

Acting Nationals leader David Littleproud condemned Mr Christensen's comments and said he had spoken with his colleague.

"(It) was an error of judgment for him to go on that program," Mr Littleproud said.

"I have asked him to reflect on that, and his judgment around having an interview with a US commentator that has somewhat of a chequered past."

The Queensland MP, who is retiring at the next election, previously compared restrictions to the regimes of Adolf Hitler and Pol Pot during a speech in parliament, and also urged civil disobedience.

Senator Gallagher said the comments were indicative of a pattern of behaviour from Mr Christensen and urged Mr Morrison to bring him into line.

"(Mr Christensen) has consistently been out spreading disinformation, misinformation, stoking division and fear," she said.

"It's got to a point when the prime minister should be taking action. I can't imagine a situation under any other prime minister where a member of their own government would be allowed to be free-range like this."

However, Nationals senator Matt Canavan said he did not have a problem with Mr Christensen appearing on InfoWars.

"Just because you go on a show, doesn't mean you agree with everything," he told Sky News.

"People are free, of course, to protest ... Australian government policies, wherever they are in the world."

Australian Associated Press