Lachlan Murdoch, co-chairman and chief executive officer of Fox Corp., attends the annual Allen and Co. Sun Valley media conference in Sun Valley, Idaho
Lachlan Murdoch, co-chairman and chief executive officer of Fox Corp., attends the annual Allen and Co. Sun Valley media conference in Sun Valley, Idaho, U.S., July 11, 2019.

Fox Corp CEO Lachlan Murdoch has filed a defamation lawsuit against an Australian news site over an opinion piece he says accused him of being complicit in the Jan. 6 attack on the U.S. Capitol by supporters of former President Donald Trump.

The lawsuit was filed on Tuesday in the Federal Court of Australia against the publisher of online masthead Crikey, its editor and the opinion piece's author. The June 29 article described the Murdochs as "unindicted co-conspirators" in the effort by Trump supporters to overturn his 2020 election loss to President Joe Biden, according to the lawsuit.

"Murdoch has been gravely injured in his character, his personal reputation, and his professional reputation," the 40-page lawsuit added. It did not specify what damages Murdoch was seeking.

A spokesperson for Murdoch, a son of Rupert Murdoch and also co-chairman of News Corp, declined to comment in addition to the filed lawsuit since the matter was before court.

In a statement on Crikey's website on Wednesday, editor Peter Fray and the chairman of its publisher Private Media, Eric Beecher, said they stood by the story and looked forward to defending their journalism in court.

"We are determined to fight for the integrity and importance of diverse independent media in Australian democracy," they wrote.

The lawsuit could become a test case for changes to Australian defamation law made in 2021 that allow defendants to claim their work was in the public interest, even if they cannot prove their allegations are true.

Private Media lawyer Michael Bradley told Reuters that the publisher was still considering the statement of claim, for which it has 28 days to file a defence.

The lawsuit would make Murdoch one of the first people to sue for defamation in Australia since the introduction of a requirement to explicitly prove "serious harm" resulted from the article, a provision put in place last year to prevent trivial claims.

Murdoch's filing said the article caused harm to his reputation by advertising it widely and wrongly suggesting he "illegally conspired with Donald Trump to overturn the 2020 presidential election", among other things.

Crikey is an online-only publication that claims 20,000 subscribers who pay A$199 ($141) a year each.

The dispute between a member of one of the world's most powerful media families - Fox Corp's main shareholder - and the relatively small Australian title comes as the Murdoch stable of businesses deals with legal challenges elsewhere over its political news coverage.

In the United States, Fox News faces a $1.6 billion defamation lawsuit brought by Dominion Voting Systems Inc accusing the company of amplifying false theories in its broadcasts that the voting machine company rigged the 2020 election so Republican Trump would lose to Democrat Joe Biden. That lawsuit names Rupert and Lachlan Murdoch as being ultimately responsible for the claims.

A U.S. congressional committee is holding hearings on the assault on the U.S. Capitol by thousands of Trump supporters. Four people died on the day of the attack and some 140 police officers were injured, one of whom died the next day.