RUPERT Murdoch has announced he will step down as chairman of News Corp and the Fox Corporation.

The multibillionaire media mogul announced the news to staff in a memo.

His son Lachlan Murdoch will succeed the 92-year-old as chair of both companies.

Rupert Murdoch will be appointed as "chairman emeritus" of both companies.

News Corp was founded in its initial form by the Australian media magnate in 1980 and grew to be the largest media company in the world – acquiring The Times and The Sun during its meteoric rise – before it was spun off into 21st Century Fox and News Corporation in 2013.

In his message to employees, Rupert Murdoch wrote: "For my entire professional life, I have been engaged daily with news and ideas, and that will not change.

“But the time is right for me to take on different roles, knowing that we have truly talented teams and a passionate, principled leader in Lachlan who will become sole chairman of both companies.

“Our companies are in robust health, as am I. Our opportunities far exceed our commercial challenges.

"We have every reason to be optimistic about the coming years – I certainly am, and plan to be here to participate in them.

“In my new role, I can guarantee you that I will be involved every day in the contest of ideas. Our companies are communities, and I will be an active member of our community.”

In a statement, Lachlan Murdoch said: "On behalf of the Fox and News Corp boards of directors, leadership teams, and all the shareholders who have benefited from his hard work, I congratulate my father on his remarkable 70-year career.

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“We thank him for his vision, his pioneering spirit, his steadfast determination, and the enduring legacy he leaves to the companies he founded and countless people he has impacted.

“We are grateful that he will serve as chairman emeritus and know he will continue to provide valued counsel to both companies.”

'It's The Sun Wot Won It'

Rupert Murdoch launched his media career in 1954 by taking control of Australian publisher News Limited, which was previously run by his father Sir Keith Murdoch.

The group rapidly expanded internationally, which included a deal to buy the News of the World and Sun newspapers in the UK in 1969.

In 1986, he launched the Fox Broadcasting company in the US and started the Fox News station ten years later. It is now the most popular news network in the US.

He is a deeply controversial figure, with critics accusing his outlets of entrenched right-wing bias. 

In 1986, Rupert Murdoch crushed the printers' union in what would become known as the Wapping dispute when workers bound for redundancy went on strike over massive job cuts at the plant which printed the News Corp newspapers. 

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The media mogul wanted to replace out-dated "hot metal" print methods with the latest computer-aided manufacturing techniques, which put 90% of that workforce out of jobs. 

His success was also a major victory for Margaret Thatcher in crushing the influence of trade unions. 

He was a hands-on editor while involved in the day-to-day running of News UK, the company which owns The Sun and published News of the World before it folded after journalists were found to have hacked phones. 

Speaking at a UK Parliament inquiry in 2007, Murdoch admitted he had exercised editorial control at The Sun and the News of the World over “major issues” – such as who to back in a general election and policy on Europe – but insisted he never interfered with the lines taken by The Times and The Sunday Times.

Murdoch closed News of the World after it emerged journalists at the title had hacked the answering machine of the murdered 13-year-old's mobile phone. 

Journalists had deleted messages to free up space for new ones, and the ensuing controversy ended the run of the 168-year-old tabloid in 2011. 

His influence in UK politics at its height was unrivalled and careers were made and destroyed by Murdoch titles, best summed up in the defeat of Labour's Neil Kinnock in the 1992 election. 

The Sun's front page the day John Major clung onto power declared: "It’s The Sun Wot Won It".