The chairman of Viacom International said Mr Murdoch's power to contravene rights enshrined in the US First Amendment lay in his role as a "gatekeeper" - controller of an organisation which controls access to systems that deliver programming.
Mr Murdoch is owner or part-owner of the Sun, Times and Sunday Times, BSkyB and Star TV, the rapidly growing Asian satellite network. His interests also include Fox, the American national TV network, a Hollywood movie studio and stakes in Australian broadcasting.
Apart from Ted Turner, the communications magnate, Mr Redstone is seen as the only global media player who could rival Mr Murdoch.
Viacom owns Paramount, the Hollywood studio, the Blockbuster Video chain, MTV Networks, which produces the music video network MTV, and VH-1, a version of MTV for older viewers. Until recently it also owned Madison Square Garden.
Mr Redstone criticised Mr Murdoch for controlling distribution of programmes in Europe and Asia and expressed concern about his control of British broadcasting.
The 73-year-old New Englander, who built his empire from a tired string of cinemas, said that while Viacom owned all of the US-based Nickelodeon, the children's cable network, it had been forced to concede 50 per cent to Mr Murdoch in Britain.
"The reason Murdoch owns 50 per cent is that we couldn't have got a distributor in England any other way," he explained.
The Viacom chairman also attacked Mr Murdoch for his efforts to extend the shelf-life of satellite against the threat from cable, saying he had offered cable operators low rates to tie up programming in the long term because he was concerned about the competition.
Mr Redstone said: "He really has got a stranglehold on the market and is finally attracting a lot of scrutiny. Cable would be a competitor except that he's buying up cable programming by giving special rates.
"There's nothing wrong with mergers or wanting to be bigger. The question is how you use that power," he said.