BORIS Johnson was last night under heavy fire after backing his chief aide despite growing calls from his backbenches to sack Dominic Cummings following allegations he breached lockdown restrictions.

Just 20 minutes after the Prime Minister had ended his briefing, where he bullishly defended Cummings, the UK Civil Service put out an angry message.

In an unprecedented post, its official Twitter account said: “Arrogant and offensive. Can you imagine having to work with these truth twisters?”

The tweet was live for about 10 minutes and received 37,000 “likes” and 25,000 “retweets” before being deleted.

READ MORE: UK Civil Service twitter says Boris Johnson is 'arrogant and offensive'

Speaking at the daily Downing Street coronavirus briefing, Johnson said Cummings had “acted responsibly, legally and with integrity”.

Conservative MPs had been calling or Johnson to dispense with Cummings after it emerged he had travelled 260 miles to County Durham in March to self-isolate with his wife and child while official rules said to “stay at home” to stop the spread of the virus and save lives.

The aide said he had travelled to the English city to seek help with childcare after his wife fell ill with Covid and in case he also became sick.

Further reports also suggested Cummings took a second trip to the North East of England in April, having already returned to London.

Cummings denied the fresh allegations, which were reported by the Observer and the Sunday Mirror, and Johnson announced he would be standing by his most senior aide.

Leading the Government press conference for just the third time since being discharged from hospital on April 12, Johnson said he could “not mark down” Cummings for the way he acted.

The PM said: “I have had extensive face-to-face conversations with Dominic Cummings and I have concluded that in travelling to find the right kind of childcare, at the moment when both he and his wife were about to be incapacitated by coronavirus – and when he had no alternative – I think he followed the instincts of every father and every parent.

“And I do not mark him down for that.

“Though there have been many other allegations about what happened when he was in self-isolation and thereafter, some of them palpably false, I believe that in every respect he has acted responsibly and legally and with integrity and with the overwhelming aim of stopping the spread of the virus and saving lives.”

Responding to the PM, Labour leader Sir Keir Starmer called for an inquiry into the saga,

“This was a test of the Prime Minister and he has failed it. It is an insult to sacrifices made by the British people that Boris Johnson has chosen to take no action against Dominic Cummings,” he said.

“The public will be forgiven for thinking there is one rule for the Prime Minister’s closest adviser and another for the British people.

“The Prime Minister’s actions have undermined confidence in his own public health message at this crucial time.

“Millions were watching for answers and they got nothing. That’s why the Cabinet Secretary must now launch an urgent inquiry.”

Speaking to BBC yesterday, the former Durham chief constable Mike Barton said Cummings had broken the rules.

He said: “Millions of people over the last two months have made great sacrifices, sacrifices looking after their family in really frustrating circumstances, businesses have gone bust, people who run businesses haven’t been able to do certain things.

“And that’s why I was really quite surprised to learn that somebody who has made the rules that are very clear that if you’re suffering from coronavirus, you have to stay at home, you’re in lockdown, you do not leave your home under any circumstances.

“Not only did they do that and travel 260 miles, but also have then tried to justify it and evade their responsibility through the use of weasel words. I find it quite shocking really.”

Barton went on to say he was “angry” and “worried” that Durham Constabulary had been embroiled in a dispute with No 10, praising the force for its handling of the situation.

“Let’s not beat about the bush, he broke the rules, it’s very clear. Now what they’re trying to do is use this sophisticated sophistry to suggest that if you’ve got a child then the rules don’t quite apply – that’s rubbish,” he added.

“The deputy chief medical officer, who’s been a beacon of wisdom for me in all of this, made it really clear, it’s got to be a life-threatening issue that allows you to break the coronavirus lockdown. This was not life-threatening.”

Backbench Tories, including prominent 1922 Committee member Steve Baker, said yesterday Cummings “must go”. Baker said: “If he doesn’t resign, we’ll just keep burning through Boris’s political capital at a rate we can ill afford in the midst of this crisis.

“It is very clear Dominic travelled when everybody else understood Dominic’s slogans to mean ‘stay at home, protect the NHS and save lives’.”

Damian Collins, Conservative MP, said: “Dominic Cummings has a track record of believing that the rules don’t apply to him and treating the scrutiny that should come to anyone in a position of authority with contempt. The Government would be better without him.”

Devi Sridhar, professor of global public health at Edinburgh University, also called for Cummings to resign.

Speaking on the Sophy Ridge show, she said: “He undermined the core public health message which was to stay home, to make sure that children are not left with elderly relatives and also going from an area that was ahead of the country – London – to an area that was a bit behind, north-east England.

“North-east England is now one of the hardest hit parts of the country ... yes, he needs to resign, but we also need to move on and bring focus to the key issues facing the UK.

“The UK now has close to 60,000 excess deaths, one of the worst death rates per capita in the world.

“We don’t have a good way out of this lockdown because there is no testing and tracing infrastructure to let us safely lift the lockdown.

“We have a lot of people suffering because of a lack of clear strategy of how we are going to move forward and get out of the deep hole that we are in.”