WASHINGTON — Media mogul Rupert Murdoch says he is stepping down as chairman of Fox and News Corp, with his son Lachlan to head both companies.

In a memo to employees, Murdoch said "the time is right" for him to take on "different roles".

Murdoch, 92, launched Fox News in 1996. It is now the most-watched TV news channel in the US.

Murdoch said he will transition to the role of Chairman Emeritus of both firms in mid-November.

"Our companies are in robust health, as am I. Our opportunities far exceed our commercial challenges," he wrote. "We have every reason to be optimistic about the coming years - I certainly am, and plan to be here to participate in them."

The transition comes during a turbulent year for Fox, which in April agreed to pay a $787.5m (£634m) settlement after being sued by voting machine company Dominion over its reporting of the 2020 presidential election. The network is still facing a second, similar lawsuit from another voting technology firm, Smartmatic, seeking an even larger sum of $2.7bn.

Then on 25 April, Fox announced it would "part ways" with Tucker Carlson, its highest rated TV host - amid reports the decision came from the very top.

The Murdoch move falls a year before the US presidential election, in which right-leaning Fox News has significant influence. The network is hosting a number of debates between Republicans vying to be the party's 2024 White House candidate.

Journalist Michael Wolff is set to release a highly anticipated tell-all book about Fox's ruling family in just a few days, titled "The Fall: The End of Fox News and the Murdoch Dynasty". A second Murdoch book, by CNN media journalist Brian Stelter, will be published on 14 November.

In his memo to staff, Rupert Murdoch vowed to continue to be involved in the "contest of ideas".

He also criticized other media outlets as being "in cahoots" with a "rarefied class" of elites who he accused of "peddling political narratives rather than pursuing the truth".

In a statement, Lachlan Murdoch - who returned to the family business in 2014 after an abrupt departure nearly a decade earlier - said that his father "will continue to provide valued counsel to both companies".

The elder Murdoch began his career in his native Australia in the 1950s, eventually buying the News of the World and The Sun newspapers in the UK in 1969.

He later purchased a number of US publications including the New York Post and Wall Street Journal. Through News Corp, he remains the owner of hundreds of local, national and international media outlets.

Until Thursday's announcement, Lachlan Murdoch had served as the executive chair of Fox Corporation and Nova Entertainment.

Fox shares rose almost 2% after the announcement, while New Corps shares rose a more modest 0.6%.

Professor Anat Alon-Beck, a corporate law expert, said that ultimately market reaction to Lachlan's promotion will depend on whether Fox has a "solid and smart" plan that ensures "that the company's leadership isn't jeopardised just because the most powerful person, CEO, leaves the role".

While Lachlan was the expected heir to the news assets, it is unclear what will happen when the elder Murdoch dies.

Any transfer of shares from Murdoch to his four adult children could potentially set the stage for a battle for the future of the media empire in which three of his offspring could out-vote a fourth. — BBC