• Video report by ITV News Political Correspondent Paul Brand

Boris Johnson has been accused of risking the Government’s efforts to combat Covid-19 in order to defend his senior aide Dominic Cummings following allegations he breached lockdown restrictions.

The Prime Minister chose to front the daily Downing Street coronavirus briefing to publicly back Mr Cummings, saying he had “acted responsibly, legally and with integrity” by driving 260 miles to County Durham to isolate and that “any parent would frankly understand what he did”.

But Tory backbenchers tore into Mr Johnson over his handling of the row, while scientists claimed that the defence of Mr Cummings’ interpretation of the lockdown rules undermined efforts to curb the spread of Covid-19.

Mr Cummings travelled to County Durham in March to self-isolate with his family while official guidelines warned against long-distance journeys, apparently because he feared that he and his wife would be left unable to care for their son.

Further reports also suggested he took a second trip to the North East in April, having already returned to London following his recovery from coronavirus.

More than 45,000 people in the UK have die after contracting the virus, according to the latest available data.

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

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The Prime Minister told a Downing Street press conference: “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.”

Mr Johnson added that “some” of the allegations about Mr Cummings’ behaviour during self-isolation were “palpably false”.

But Tory MPs criticised the Prime Minister’s actions, with former minister Paul Maynard saying he shared people’s “dismay” at the response.

“It is a classic case of ‘do as I say, not as I do’ – and it is not as if he was unfamiliar with guidance he himself helped draw up.

“It seems to me to be utterly indefensible and his position wholly untenable.”

Tory MP Peter Bone told ITV News Mr Cummings should have resigned.

"What I think is unforgivable is that Dominic Cummings didn't resign," he said.

"And then he put the prime minister in a situation where it was either sack him or keep him and, in the past, an adviser in that situation would have no hesitation but to resign."

Mr Bone added that "when advisers become the story, they go".

"Behind the scenes, the vast, vast majority of Conservative MPs think Dominic Cummings should go," he said.

A tweet posted by the UK Civil Service, soon deleted. Credit: Twitter

A tweet posted from the UK Civil Service account, which was quickly deleted, said: "Can you imagine having to work with these truth twisters?"

The Cabinet Office, commenting on the tweet, said: "An unauthorised tweet was posted on a government channel this evening.

"The post has been removed and we are investigating the matter."

  • What happened and when: A timeline

Scientists advising the Government also strongly criticised the Prime Minister.

Social psychologist Professor Stephen Reicher, one of the scientists on the Scientific Pandemic Influenza Group on Behaviours (SPI-B) said Mr Johnson had “trashed” their advice.

“As one of those involved in SPI-B, the Government advisory group on behavioural science, I can say that in a few short minutes tonight, Boris Johnson has trashed all the advice we have given on how to build trust and secure adherence to the measures necessary to control Covid-19.

“Be open and honest, we said. Trashed. Respect the public, we said. Trashed Ensure equity, so everyone is treated the same, we said. Trashed. Be consistent we said. Trashed. Make clear ‘we are all in it together’. Trashed.

“It is very hard to provide scientific advice to a government which doesn’t want to listen to science.”

His views were echoed by colleagues on the SPI-B group.

Labour leader Sir Keir Starmer said Mr Johnson has treated the British public with “contempt” by not sacking Mr Cummings - making this the first time Labour has called for the chief adviser to go.

Speaking outside his home in north London, Mr Starmer said: “This was a huge test of the Prime Minister and he’s just failed that test, he hasn’t sacked Dominic Cummings, he hasn’t called for an investigation and he’s treating the British public with contempt.

“Millions of people across the country have made the most agonising choices not to visit relatives, some of whom were ill, dying, not to go to funerals.

“They deserve better answers than they got from the Prime Minister today.”

Dominic Cummings has been under pressure over his travel. Credit: PA

Footage posted on social media showed Mr Cummings being heckled by a crowd of onlookers as he returned to his home in London.

One woman could be heard shouting: “My mum’s terrified, my dad’s had three shoulder operations… she won’t even entertain me in her garden with a tent.”

The woman, who was filming Mr Cummings on her phone as she spoke, could then be heard telling him: “I’m a single parent. I’ve had no childcare since the beginning of this whole mess, not that I can afford to pay any child care.

Another shouted: “Would you recommend Barnard Castle for a day out?”

Mr Cummings appeared not to respond to the heckling. As he entered his home, shouts of “hypocrite”, “resign” and “shame” could be heard from the group, which did not appear to be associated with the assembled media.

  • How the public has reacted to Dominic Cummings's alleged breach of the lockdown rules

Over the weekend, Number 10 admitted Mr Cummings had driven from his London home to Durham in March after his wife started displaying Covid-19 symptoms, becoming fearful there would be no-one to look after his four-year-old child if he also took ill.

But according to reports, the former Vote Leave campaign co-ordinator made a second trip to Durham and was seen there on April 19, five days after being photographed on his return to Westminster.

A second witness told the papers they saw him a week earlier in Barnard Castle on Easter Sunday, a popular tourist location 30 miles from Durham.

Boris Johnson did not deny claims that Dominic Cummings visited Barnard Castle in April.

Coronavirus: Everything you need to know