LONDON, ENGLAND -- Rupert Murdoch said on Monday he had never asked a British prime minister for anything, seeking to play down his influence ahead of what is likely to be a politically charged approval process for his purchase of the pay-TV group Sky.

The 85-year-old's Twenty-First Century Fox (FOXA.O) made a formal approach to take full control of the British-based Sky last week, reigniting a row over whether the media mogul controls too much of Britain's media.

In a short letter to the Guardian newspaper on Monday, Murdoch said he had never asked a prime minister for anything.

"On a number of occasions now your paper has quoted me as saying: 'When I go into Downing Street, they do what I say; when I go to Brussels, they take no notice,'" Murdoch wrote.

"There is much fake news published about me, but let me make clear that I have never uttered those words. I have made it a principle all my life never to ask for anything from any prime minister."

The letter, signed: Rupert Murdoch, New York, USA, was published on the Guardian website.

Murdoch's previous attempt to buy the 61 per cent of Sky he did not already own was scuppered in 2011 by a phone-hacking scandal at one of his tabloid newspapers.

The British government will have to decide in the new year whether to refer the new bid for further scrutiny by the media regulator Ofcom.