CNN founder Ted Turner attacked US TV network Fox News on Tuesday, labelling it "propaganda" for its stance towards the Bush administration.
Ted Turner said media companies were not being critical enough
Turner also likened the network's current popularity to Adolf Hitler's rise to power in 1930s Germany.
"Just because you're bigger doesn't mean you're right," Turner said in a speech to the National Association of Television Programming Executives.
Fox News, owned by Rupert Murdoch, is currently leading CNN in TV ratings.
Mr Turner also attacked "gigantic companies whose agenda goes beyond broadcasting" for not criticising the Bush administration enough.
"There's one network, Fox, that's a propaganda voice for them," the 66-year-old media mogul said.
"It's certainly legal. But it does pose problems for our democracy when the news is 'dumbed-down'."
Fox News issued a statement, saying: "Ted is understandably bitter having lost his ratings, his network and now his mind - we wish him well."
During a question-and-answer session, Mr Turner, who stood down as the chairman of AOL Time Warner in 2003, said it was "not necessarily a bad thing" that CNN and other news networks were behind Fox in the ratings.
Fox News is owned by Australian-born tycoon Rupert Murdoch
"Adolf Hitler was more popular in Germany in the early 1930s than people that were running against him," Mr Turner said.
A spokesman from the convention said the organisers had no comment about the media magnate's comments.
Mr Turner, the former husband of actress and peace campaigner Jane Fonda, heads an Atlanta-based business and media empire.
Fox News was recently the subject of a documentary film, Outfoxed, which attacked its slogan of "fair and balanced" news.