The billionaire mogul on Friday said he was retiring as chair of both Fox Corporation and News Corp after a media career of nearly 70 years.

But at the age of 92, Murdoch said he was still in “robust” health, as were his companies.

He will become ‘chairman emeritus’ of both companies while Lachlan will become News Corp chairman and continue as chief executive officer of Fox Corp.

In a memo to employees, Murdoch promised he would remain “involved every day in the contest of ideas”.

“For my entire professional life, I have been engaged daily with news and ideas, and that will not change,” Murdoch wrote.

“But the time is right for me to take on different roles, knowing that we have truly talented teams.”

There was no immediate word on why Murdoch’s announcement came now.

Murdoch also took aim at “elites” and sections of the media as he said the battle for freedom of speech had “never been more intense”.

“Self-serving bureaucracies are seeking to silence those who would question their provenance and purpose,” the memo read.

“Elites have open contempt for those who are not members of their rarefied class.

“Most of the media is in cahoots with those elites, peddling political narratives rather than pursuing the truth.”

Lachlan Murdoch said his father “will continue to provide valued counsel to both companies.”

The news comes in a rough year for Fox which was forced to pay $US787 million ($1.3 billion) to settle a defamation lawsuit brought by voting machine company Dominion over false coverage.

Shortly after, Fox fired its most popular host Tucker Carlson.

Ironically, next week author and Murdoch biographer Michael Wolff is publishing a book, The End of Fox News, speculating on what will happen to the network when the patriarch is gone.

Murdoch and his family, particularly children James, Lachlan, Elisabeth and Prudence, were said to be the model of the HBO show Succession.

Forbes estimated the Murdoch family’s net worth at roughly $US19 billion in 2020 ($30 billion).

Murdoch built his empire from a single newspaper, The News, in Adelaide which he inherited from his father in the 1950s.

He established The Australian newspaper a decade later, and also bought the The Sun and now-defunct News of the World tabloids in Britain.

In 1976 he added The New York Post, followed in the 1980s by The Times newspaper and Harper Collins book publishers before the company acquired The Wall Street Journal in 2007.

Murdoch’s foray into entertainment in the US, where he became a naturalised US citizen to allow him to satisfy the requirements to own US television networks, was where his empire expanded its reach.

In 1985 News Corporation bought Twentieth Century Fox Film Corporation, which later branched into Fox News and Fox Sports.

Besides Fox News, Murdoch started the Fox broadcast network, the first to successfully challenge the ‘big three’ of ABC, CBS and NBC.

He slimmed down his corporate holdings with the 2019 sale of many entertainment assets to the Walt Disney Co. These included film production, rights to the Marvel comics, National Geographic and the cable network FX.

Fox News Channel has profoundly influenced television and the nation’s politics since its start in 1996, making Murdoch a hero to some and pariah to others. The 24-hour network converted the power and energy of political talk radio to television. Within six years, it outrated CNN and MSNBC.

While Murdoch never ran for political office, politicians in the United States and Britain anxiously sought his approval. He had a complicated relationship with Donald Trump.

Wolff reported in 2018 that Murdoch had called Trump an “idiot,” adding an expletive for emphasis, but Fox News is built with an audience that largely admires Trump.

Fox briefly seemed to tout the candidacy of Florida Governor Ron DeSantis in the current election cycle, but that has faded along with DeSantis’ prospects.

For decades, Murdoch was one of the most powerful media figures in Britain, a market he entered after buying the tabloid News of the World in 1969. He reinvigorated Britain’s stodgy newspaper scene with sex, scandal and celebrity and helped shake up television with satellite broadcaster Sky.

His clout has waned since the revelation more than a decade ago that employees of the News of the World had eavesdropped on phones and used other underhanded methods to get scoops on celebrities, politicians and royals.

News Corp owns the Times, Sunday Times and Sun newspapers, but News of the World closed and Murdoch sold his 40 per cent stake in Sky when he failed to get complete control of the company.

–The New Daily/AAP