Scotland Yard criticised his behaviour as “plainly disappointing” but ruled out issuing a fine because he “has taken responsibility” after resigning as a key Government adviser in the coronavirus response.
Mr Johnson's spokesman said the PM "agrees" with Prof Ferguson's decision to resign from Sage, adding how his membership on Nervtag (the new and emerging respiratory virus threats advisory group) had also been relinquished.
Health Secretary Matt Hancock said the Imperial College London professor had made the “right decision to resign” but that it was a matter for police to decide whether to take further action.
Scotland Yard said: “We remain committed to our role in supporting adherence to Government guidance and have made it clear that our starting position is explaining the need to follow the regulations with anyone who is in breach in order to keep people safe and protect the NHS.
“It is clear in this case that whilst this behaviour is plainly disappointing, Professor Ferguson has accepted that he made an error of judgment and has taken responsibility for that.
“We therefore do not intend to take any further action.”
The Metropolitan Police declined to say whether officers had spoken directly to Prof Ferguson.
Number 10, in a briefing with reporters on Wednesday, denied the Government had put pressure on the Imperial College London academic to stand down.
The Prime Minister’s official spokesman said: “We were informed by the Government’s office for science yesterday evening.
“I think we were informed just before (the story broke) and we were told that Professor Ferguson had offered to step back.”
Police spoke to Dr Calderwood and issued her with a warning after the breach was made public.
The latest data shows more than 9,000 fines have been issued across England and Wales for flouting lockdown rules.
The Telegraph reported that Prof Ferguson allowed 38-year-old Antonia Staats, said to be his “lover”, to visit him at home in London at least twice during the lockdown.
Mr Hancock said he was speechless after learning of Prof Ferguson’s “extraordinary” actions.
The Cabinet minister praised him as a “very eminent” scientist whose work has been “important” in the Government’s response, but said he had to resign.
Asked about police involvement, Mr Hancock told Sky News: “Even though I have got a clear answer to what I think, as a minister the way we run the police is that they make decisions like this.
“So I give them their space to make that decision, but I think he took the right decision to resign.”
Prof Ferguson’s research warned that 250,000 people could die in the UK without drastic action before the Prime Minister imposed restrictions, ordering the public to stay at home as he shut most shops and gave police unprecedented enforcement powers.
Under those measures, partners who do not live together were told they can no longer see each other.
The paper said merely slowing the spread of the virus - which had at that point been the aim - would have led to the NHS being overwhelmed by Covid-19 cases.
In a statement on Tuesday night, Prof Ferguson said: “I accept I made an error of judgment and took the wrong course of action. I have therefore stepped back from my involvement in Sage.
“I acted in the belief that I was immune, having tested positive for coronavirus, and completely isolated myself for almost two weeks after developing symptoms.
“I deeply regret any undermining of the clear messages around the continued need for social distancing to control this devastating epidemic. The Government guidance is unequivocal, and is there to protect all of us.”
Prof Ferguson said on March 18 that he had the fever and cough symptoms of Covid-19 and there was a small risk he had infected others in highlighting “the need for the response which has been enacted”.
Speaking on BBC Radio 4’s Today programme in April, Prof Ferguson had stressed the importance of keeping to social distancing guidelines.
He said at the time: “If we want to reopen schools, let people get back to work, then we need to keep transmission down in another manner
“It is not going to go back to normal, we will have to maintain some level of social distancing – significant levels of social distancing – probably indefinitely until we have a vaccine available.”
Mr Hancock, who himself has overcome Covid-19, said the science is not yet conclusive as to whether surviving an infection means there is a low risk of spreading the virus.
“Everyone has got to follow the social distancing rules,” he responded, shaking his head, when asked if Prof Ferguson could return to the role if immunity was proved.
Imperial College London said Prof Ferguson “continues to focus on his important research”.
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