CNN has cut ties with a conservative commentator hours after he tweeted a Nazi salute at a prominent liberal activist.

A CNN spokesperson said in a statement: “Nazi salutes are indefensible. Jeffrey Lord is no longer with the network.”

Mr Lord tweeted “Sieg Heil” in response to an exchange with Angelo Carusone, the president of Media Matters for America, causing an uproar on social media.

Mr Lord and Mr Carusone have had many sharp disagreements. Mr Lord, also a columnist for The American Spectator, has harshly criticised Media Matters, and the organisation has frequently blasted CNN for employing Mr Lord as a commentator.

Earlier this week, the two men got into a heated debate on Twitter over Media Matters’ past financial support from investor and business magnate George Soros.

Mr Carusone told Mr Lord that one of his columns was “full of lies” and said “Soros gave us one donation one time...in 2010.”

Mr Lord published another column on Thursday in which he called Mr Carusone's group the “Media Matters Fascists”, casting the organisation's members as “anti-free speech bigots who, in typical fascist style, make it their mission to shut down speech they don't like.”

Media Matters has been promoting an ad boycott against Fox News TV host Sean Hannity, a friend of Mr Lord’s and a staunch supporter of Donald Trump.

Mr Lord said Mr Carusone was playing a “fascist game” by targeting Mr Hannity's sponsors.

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“This is America, Angelo. Not Fascist Italy, Nazi Germany or Communist Russia,” he wrote.

Mr Lord tweeted the column at Mr Carusone, whose name had been misspelt as “Corusone” in the headline. Mr Carusone responded: “Your headline has a mistake in it. Why do you expect anyone to take you seriously when you don't take yourself seriously.”

Mr Lord replied, “Sieg Heil!”

Mr Lord later defended his tweet, saying he was mocking Nazis and fascists and refused to backtrack his comment.

In a telephone interview with CNN, Mr Lord said, “I think these people are very dangerous,” referring to Media Matters.

“They run around bullying people, bullying advertisers to take people off the air,” he added.

Regarding the offensive tweet, he said, “I'm mocking people who are posing a serious threat to the American free press. That's what I'm mocking.”

“I love CNN, but I feel they are caving to bullies here,” he also told the network.