Newsnight host Emily Maitlis stated as fact that the Prime Minister’s top aide had not followed the rules after he took a 260-mile trip from London to County Durham with his family.
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In a scathing monologue, she insisted Mr Cummings was in the wrong, despite the Vote Leave organiser insisting he had followed the rules.
Her comments have now sparked an impartiality row.
She had said: “Dominic Cummings broke the rules, the country can see that, and it's shocked the government cannot.
“He should understand that public mood now. One of fury, contempt and anguish.
'He made those who struggled to keep to the rules feel like fools, and has allowed many more to assume they can now flout them.”
Tory grandee Iain Duncan Smith bashed her comments, and warned it was not the job of presenters to offer a personal opinion.
He told The Sun: “It’s quite wrong of an interviewer to express their own views using a platform they have been fortunate to get.
“The charter is very clear that the BBC is not to express its own personal opinions.”
Tory MP Michael Fabricant said: "The BBC is supposed to present news in an unbiased way without a personal commentary.
"Newsnight is meant to do just that: present news and interviews. Not the personal views of its presenters.
"The BBC seems to be losing all its values as a national public broadcaster."
Former Labour MP and Brexiteer Kate Hoey added: "Understand that the BBC is being inundated with complaints about Emily Maitlis and Newsnight from last night.
"I have also put in a complaint and am sure many many more will #bbcbias".
The comments also prompted a backlash from the public on social media.
One wrote: “What a totally disgraceful speech from Emily Maitlis and the BBC Newsnight editorial team.
“Ofcom need to step in because the BBC are clearly breaking their own charter. This in nasty and not at all unbiased or impartial.
Another said: “This is a presenter's opinion and using her position to give her viewpoint. We deserve as taxpayers to have impartial broadcasters.”
Boris Johnson has so far refused to sack Mr Cummings despite a Tory civil war breaking out.
The PM again stood by his chief aide who is accused of twice breaking lockdown rules to travel with his family.
A press conference on Monday by Mr Cummings giving his side of the story failed to quell anger. Scotland Office minister Douglas Ross resigned in protest.
Almost 40 backbench Tory MPs have also publicly called for the Vote Leave guru to step down.
Some have been spooked by polls showing the PM’s approval rating has plummeted by 20 per cent and that more than half of the public think Mr Cummings should quit.
A Savanta ComRes poll shows Mr Johnson’s rating has dropped to minus one.
The government’s approval is down by 16 per cent.
And a YouGov poll shows 71 per cent of Brits say Mr Cummings did break lockdown and 59 per cent think he should resign.