GB News has been plunged into crisis as news of a senior executive’s resignation emerged hours after a presenter was taken off air for symbolically taking the knee on screen, the Guardian has learned.

The rightwing TV channel is contending with other staff considering leaving amid management upheaval, collapsing ratings and plans for a relaunch after Guto Harri was “cancelled” by its viewers.

John McAndrew, the channel’s director of programming, has also quit the station, sources told the Guardian. McAndrew, a well-known figure in the television news industry who has a long track record at mainstream outlets including Sky News and Euronews, was considered to be the channel’s second-in-command and played a key role in convincing many of the more established mainstream presenters to join.

Sources suggested he had come under pressure to dial down the focus on local reporting and free debate in favour of full-blooded culture war topics, so chose to resign.

GB News was unable to withstand the strong and sustained viewer backlash to Harri’s display of solidarity against the racist abuse suffered by the England football team.

The channel, set up on the basis that free and open debate is no longer possible in the mainstream media due to an all-pervasive “cancel culture”, was overwhelmed with complaints that after only a few weeks on air it had gone “woke” and its content was not sufficiently rightwing.

After three days and a growing boycott, which led to some shows attracting zero viewers, the channel’s management felt the need to cut Harri loose. In a statement, GB News said it was “unacceptable” for any presenter to take the knee, a symbol associated with the Black Lives Matter movement, and said Harri had broken the channel’s editorial code.

Friends of Harri said: “GB News is becoming an absurd parody of what it proclaimed to be – not defending free speech and combatting cancel culture but replicating it on the far right. Nasty.

“It’s ridiculous to say he’s breached editorial standards and almost certainly defamatory. In reality it wasn’t a breach of editorial code but ‘sacked for offending the lynch mob’.”

It is unclear which part of the GB News editorial code Harri could have broken. The channel’s public editorial charter commits itself to core values including “independence of our journalism”, “respect for opinions and those expressing them”, and “the right of every individual to form and share their views”.

A spokesperson for GB News was unable to immediately confirm whether Harri would be leaving the channel, and refused to comment on McAndrew’s departure.

The incident comes amid a growing crisis at the channel, which launched only four-and-a-half weeks ago. Some senior off-air staff are understood to have left in recent days amid ongoing turmoil following the channel’s disastrous launch, which was plagued by technical difficulties.

They include Gill Penlington, a respected and experienced producer at rolling news channels such as CNN and Sky News who has worked in the past with the GB News chairman, Andrew Neil. She was brought in as a senior figure before launch, only to leave earlier this week. The departure of other key off-air figures could be announced imminently, according to sources at the channel.

There is also strong speculation about Neil’s current relationship with the channel. He was involved with its creation and is chairman of its board, and the station was counting on his flagship 8pm show to bring in the viewers required to make it a success. However, after two weeks on air he has taken an extended holiday in the south of France.

On Friday night Neil tweeted about the station for the first time in almost two weeks, saying: “Start ups are fraught and fractious. @GBNEWS is no exception. But the news channel is finding its feet and has a great future. Watch this space.”

The station’s misery was compounded after host Alastair Stewart revealed on Friday he had broken his hip in a horse-riding accident. The veteran broadcaster tweeted he would be out for “a while” but pledged “I’ll be back”. Stewart also thanked GB News staff for their “kindness and support”.

He tweeted: “I was leading in one of the horses & she bolted, knocking me over – rather forcefully!”

The Harri incident has proved indicative of the issues facing GB News. Harri was a longserving BBC correspondent before moving into politics as Boris Johnson’s spokesperson during his first term as mayor of London. He then went to work for Rupert Murdoch’s News UK for several years, yet has found himself portrayed by some GB News viewers as a dangerous leftwing Marxist sleeper agent.

There is particular upset among the GB News staff who earlier this week publicly defended Harri’s right to freedom of speech, only to find their stance later contradicted publicly by management.

Staff describe a split between two broad camps. Some producers and presenters come from a mainstream broadcast journalism background and felt jumping ship to the new channel would give them a fresh challenge or a career boost. Others are approaching it from a more political angle with a personal commitment to culture war topics. In Neil’s absence, the only show with relatively healthy ratings has been Dan Wootton’s late-night show, which has lent heavily into culture war issues.

Neil had made clear before the channel’s launch that he did not want to be a “British Fox News” and would be committed to traditional journalism values albeit with a rightwing twist. However, this appears to be different to what its audience wanted.

As David Kurten, a former Ukip politician who now leads the niche rightwing Heritage party, gleefully tweeted at the channel after Harri took the knee: “Go woke, go broke.”