WASHINGTON, United States (AFP) — The White House war on the press took a new turn with the banning of a CNN reporter, marking a tense new phase in the long-running battle between President Donald Trump and his chief media antagonist.

The ban on CNN’s Jim Acosta came after a heated exchange at a White House news conference Wednesday where Trump called the TV reporter a “rude, terrible person” and an “enemy of the people.”

White House press secretary Sarah Sanders announced the decision to revoke Acosta’s pass hours after the event, claiming it was because Acosta was inappropriately “placing his hands” on a woman who was taking back a microphone.

She tweeted a video purportedly backing up that claim. But analysts and other journalists pointed out the video had been manipulated, sped up to make it appear he was striking the female aide.

“I think we have crossed a new line, because the reason for taking away Acosta’s credentials is a lie,” said Dan Kennedy, a Northeastern University journalism professor.

“It’s a lie that anyone who has seen the video can see for themselves. We’ve crossed into a new territory – not only is the White House going to lie but it’s going to be obvious, and they expected people loyal to them to believe it.”

The White House Correspondents’ Association said it “strongly objects” to the action, calling it “out of line to the purported offense.”

Sanders said Thursday the White House stood by its decision: “The question is: did the reporter make contact or not? The video is clear, he did.”

Jeff Mason, a Reuters journalist and former president of the association, said on Twitter: “I was seated next to @Acosta at today’s press conference and did not witness him ‘placing his hands’ on the young intern, as the White House alleges.”

The video was first shared by a contributor to the Infowars website know for promoting conspiracy theories, reports said.

CNN said “this president’s ongoing attacks on the press have gone too far,” in a statement.

“They are not only dangerous, they are disturbingly un-American.”

The White House sought to brush aside suggestions it is stifling a free press.

“Contrary to CNN’s assertions there is no greater demonstration of the President’s support for a free press than the event he held today,” Sanders tweeted. “Only they would attack the

President for not supporting a free press in the midst of him taking 68 questions from 35 different reporters.”

The incident is the latest in a series of clashes between the president and mainstream media outlets, following a spate of comments from Trump calling unfavorable coverage “fake news” and threatening to revoke credentials at some organisations.

But the skirmishes have also created an unusual kind of political theater that has boosted ratings of cable news channels and given Trump ammunition to rally his supporters.

Trump has skipped the traditional presidential appearance at the White House Correspondents Association dinner the past two years, and media organisations have been hard-pressed to respond to the attacks.

Craig Aaron of the activist group Free Press called Trump’s actions “a direct and dangerous attack on the public’s rights to hold their leaders accountable” and called for “a unified stand” by the press corps.

“If that takes a walkout, a boycott or turning off the cameras when the president is at the podium, they should do it,” Aaron said.

Media analysts said a concerted action by the press was unlikely.

“White House press corps is a beast without a brain,” tweeted New York University professor Jay Rosen.

“It cannot make decisions. Only individual news organisations, each a part of the corps, can do that. This means it literally cannot think. It has an association, the @whca but the only thing it knows is access.”