Outspoken US media tycoon Ted Turner turned up the heat in his acrimonious and long-standing feud with Rupert Murdoch last night, calling the News Corp chairman a "warmonger" for his support of the war in Iraq.

Just weeks after Mr Turner challenged Mr Murdoch to a fist fight, he waded into his old adversary for his unrelenting support of the war.

"He's a warmonger," Mr Turner said in a speech in San Francisco. "He promoted it."

Mr Murdoch openly backed the war on Iraq but the unquestioning support of his Fox News channel has caused controversy and astounded UK broadcasters, which are bound by law to maintain impartial and balanced news services.

Fox News, which is controlled by News Corp, was one of the staunchest pro-war news organisations in the US and its pro-Bush stance helped it overtake CNN, founded by Mr Turner, as the the most popular news network during the conflict.

Asked by a member of the audience for his thoughts on Fox's larger ratings share than CNN, Mr Turner said: "Just because your ratings are bigger doesn't mean you're better."

"It's not how big you are, it's how good you are that really counts," Turner added.

Mr Turner, a well-known philanthropist who in 1997 pledged to give $1bn to the United Nations, echoed criticisms levelled yesterday at the US media by the BBC director general, Greg Dyke, who said America's concentration of media ownership was "unhealthy".

The US media baron said the control exercised by a few corporations over vast swathes of American TV, radio and print media was detrimental. "The media is too concentrated, too few people own too much," he said.

Asked whether he would again try to launch a new TV network, the AOL Time Warner vice chairman said: "No. I think the space is filled with the people already there."

Mr Turner's long-running feud with Mr Murdoch goes back to 1983 when a Murdoch-sponsored yacht ran into Mr Turner's boat during the Sydney-to-Hobart race, causing it to sink 10km from the finish line.

At the post-race dinner Mr Turner savaged Mr Murdoch, later challenging him to a televised fist-fight in Las Vegas.

When Mr Murdoch launched Fox News in 1996 as a direct competitor to CNN, Mr Turner said he was "looking forward to squishing Rupert like a bug".

He also compared his rival to Adolf Hitler. "How do you make peace with a mega-maniac?" Mr Turner once said of Mr Murdoch. "Chamberlain tried to make peace. When you've got somebody like that, I don't think there's a spark of human decency in him - except he likes his family."

Throughout the war of words Mr Murdoch has hit back through his newspapers, with the New York Post claiming Mr Turner was "veering dangerously towards insanity" and asking readers, "Is Ted nuts? You decide."