A senior CNN executive on Thursday said that the video distributed by the White House to support its argument for banning reporter Jim Acosta had been “doctored”.

The White House on Wednesday revoked the press pass issued to CNN correspondent Acosta “until further notice” after a tense interaction between United States President Donald Trump and Acosta. Trump had called the reporter a “rude and terrible person” after Acosta shot several questions at him during a post midterm election press conference.

But White House Press Secretary Sarah Sanders claimed that Acosta had “placed his hands” on an intern who had attempted to take the microphone away from him. Acosta called the claim a “lie”.

CNN Vice President of Communications and Digital Partnership Matt Dornic said it was “absolutely shameful” that Sanders had released a “doctored” video. “You released a doctored video – actual fake news,” Dornic tweeted. “History will not be kind to you.”

Sanders tweeted the video, which shows Acosta questioning Trump as the intern tries to take his microphone away. Independent video producer and expert Abba Shapiro examined the footage of the same incident shot by AP and said a frame-by-frame comparison shows that the video tweeted by Sanders appears to have been doctored to speed up Acosta’s arm movement as he touches the intern’s arm.

The video tweeted by Sanders does not have any audio, which would make it easier to tamper with, said Shapiro. It is unlikely that the differences in the videos could be explained by technical glitches or by video compression [reducing a video’s size to enable it to play more smoothly on some sites] because the slowing of the video and the acceleration that followed are “too precise to be an accident”, said Shapiro.

The video was allegedly originally made by an employee of Infowars, a far-right conspiracy website, The Guardian reported.

Despite the video’s veracity being questioned, Sanders on Thursday reiterated that the administration will stand by its decision to revoke Acosta’s hard pass. “We will not tolerate the inappropriate behaviour clearly documented in this video,” she said.

CNN said in a statement that Acosta has the network’s full support. The channel said the revocation “was done in retaliation for his [Acosta] challenging questions”. “This unprecedented decision is a threat to our democracy and the country deserves better,” CNN said.

The White House News Photographers Association said it was “appalled” to learn that Sanders may have shared a doctored video. “As visual journalists, we know that manipulating images is manipulating truth,” the association said in a statement. “It’s deceptive, dangerous and unethical. Knowingly sharing manipulated images is equally problematic, particularly when the person sharing them is a representative of our country’s highest office with vast influence over public opinion.”

Several journalists and organisations, including the American Society of News Editors, the Associated Press Media Editors and the Online News Association, have demanded that the White House reinstate Acosta’s press pass.

“Journalists should be able to do their job without fear that a tough series of questions will provoke retaliation,” said Committee to Protect Journalists’ Advocacy Director Courtney Radsch in a statement. “The White House should immediately reinstate Jim Acosta’s press pass, and refrain from punishing reporters by revoking their access – that’s not how a free press works.”