Mr Cummings is accused of breaking lockdown rules after it emerged on Friday he had travelled 260 miles to County Durham in March to self-isolate with his family while official guidelines warned against long-distance journeys.
At the daily Downing Street press conference on Sunday evening, Mr Johnson said Mr Cummings had “acted responsibly, legally and with integrity”.
Downing Street has defended Mr Cummings’ actions, insisting he “acted in line with guidelines” and that his journey was “essential” because it related to the welfare of his child.
Following Mr Johnson’s defiant defence of his chief adviser, Professor Stephen Reicher tweeted that Mr Johnson had “trashed” all the advice he had been given about building public trust.
“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,” he wrote.
Prof Reicher is on the Independent Scientific Pandemic Influenza Group on Behaviours (SPI-B) which feeds analysis and advice to the scientists on the Government’s emergency panel.
In a second tweet, Prof Reicher said: “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.”
He added: “It is very hard to provide scientific advice to a Government which doesn’t want to listen to science.
“I hope, however, that the public will read our papers and continue to make up for this bad Government with their own good sense.”
Prof Reicher’s post had been retweeted more than 20,000 times in less than two hours, including by other scientists on SPI-B.
Prof Reicher, who is professor of social psychology at the University of St Andrews, said: “It feels increasingly as if we are living through a Greek drama.
“The kingmaker Cummings’ fatal flaw of hubris brings down both him and the king…what makes it tragedy is that such incompetence and turmoil will bring the people down as well.”
Another member of the panel said those tasked with spreading the lockdown message were “fighting a rear guard action constantly against government confusion and misinformation”.
Robert West, professor of Health Psychology at University College London (UCL), said: “I am sorry to have to say that as another member of SPI-B I have to agree.”
Prof West said it was imperative the public didn’t abandon social distancing despite the exceptions made for the PM’s chief aide.
“The key thing we need to remember is that the reason for the lockdown is not for the sake of people like Dominic Cummings or the Prime Minister it is four our friends and families sake so the rules are really, really important,” he said.
“There is a natural human tendency to say ‘If someone else can flout it, so can I’ but who will suffer?
“Dominic Cummings won’t suffer if we abandon it, the Prime Minister won’t suffer – it will be the people who we love who will suffer.
“That is what we need to keep in mind. What this is for and why we need to do it.
“Although we are fighting a rear guard action constantly against government confusion and misinformation we have to really keep hammering home this message.”
Prof West said scientists speaking out against the Government they are supposed to be advising “is the last thing any of us wanted to do”.
Prof West’s UCL colleague Susan Michie, director of the university’s Centre for Behaviour Change, said: “As another member of SPI-B, I completely agree.”
Prof West said everyone in SCI-B, all of whom are unpaid for their work, would be thinking “very hard” about their future on the panel.
Meanwhile, Church of England bishops have accused the Prime Minister of treating people “as mugs” and with “no respect” after he defended the lockdown actions of his chief aide.
Writing on Twitter, the Rt Revd Nick Baines, Bishop of Leeds, said: “The question now is: do we accept being lied to, patronised and treated by a PM as mugs?
“The moral question is not for Cummings – it is for PM and ministers/MPs who find this behaviour acceptable.
“What are we to teach our children? (I ask as a responsible father.)”
A few minutes earlier, the Rt Revd Dr Helen-Ann Hartley, Bishop of Ripon, commented in response to a critical tweet about the Prime Minister.
She wrote: “Integrity, trust and leadership were never there; just a driven misguided ideology of power that has total disregard for the most weak and vulnerable, and those who work to protect and care for us with relatively low pay.”
Dr Hartley also shared some details of her experience of being unable to see her parents during lockdown.
She tweeted: “My parents live in Durham, an hour away from where we live. My father finished radiotherapy treatment just before lockdown.
“I’ve missed his birthday, Mothering Sunday and countless other catch-ups that would have happened.
“And that’s a fraction of a story compared with others.”
It comes as a Durham councillor called on police to launch an investigation into whether an offence was committed by Mr Cummings when he travelled to the area.
Cllr Amanda Hopgood, the leader of the Liberal Democrat opposition on Durham County Council, said she had written to Durham Constabulary’s Chief Constable Jo Farrell after being made aware of a number of sightings of the the Prime Minister’s senior aide in the area in April and May.
She said: “We are aware that a number of local residents have reported seeing Mr Cummings in the city and county of Durham on a number of occasions during April and May and have expressed concern about the public health implications of his presence given reports that he has been affected by the coronavirus.
“Given the clear public interest in this case I have today referred this matter to the Chief Constable of Durham Constabulary to ask her force to investigate whether Mr Cummings may have committed an offence under the provisions of section 15 of the 2020 Health Protection (Coronavirus) Regulations.”
New reports from the Guardian and Mirror on Sunday evening suggest Mr Cummings is facing a possible police investigation under health laws after a member of the public made a formal police report.
Retired chemistry teacher Robin Lees has reported Mr Cummings for a suspected breach of lockdown after claiming to have seen Mr Cummings and his family on April 12 walking in the town of Barnard Castle – 30 miles from his family home.
In his report to Durham Police, seen by the Mirror, Mr Lees says: “In the light of recent information I feel that as well as an important breach of the lockdown there may also have been concerns over Health Protection Regulations.
“I assume you are able to view CCTV to ascertain whether this vehicle travelled locally or from further away.”
But Mr Johnson has defended his chief adviser, saying he has had “extensive face-to-face conversations” with him after the initial reports emerged.
Speaking at the Downing Street press briefing on Sunday, he said: “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 Shapps also told Sky’s Sophy Ridge that Mr Cummings was “trying to do the best by the child”.
He said: “What they’ve done is gone to make sure there’s a support network around them, both parents were concerned about being ill, so they’ve gone somewhere which was adjacent to his parents.
“It meant that if they were both ill that the child would be getting support.”