Boris Johnson’s senior aide Dominic Cummings said his decision to drive to County Durham was based not only on fears over a lack of childcare if he became incapacitated with Covid-19 but also concerns about his family’s safety.

At an extraordinary press conference in Downing Street’s rose garden, Mr Cummings said stories suggested he had opposed lockdown and “did not care about many deaths”.

“The truth is that I had argued for lockdown, I did not oppose it but these stories had created a very bad atmosphere around my home, I was subjected to threats of violence, people came to my house shouting threats, there were posts on social media encouraging attacks.”

Mr Cummings said he was worried that “this situation would get worse” and “I was worried about the possibility of leaving my wife and child at home all day and often into the night while I worked in Number 10.”

“I thought the best thing to do in all the circumstances was to drive to an isolated cottage on my father’s farm.”

Setting out the details of his actions, Mr Cummings said the Prime Minister had asked him to publicly give his account and he acknowledged he should have spoken earlier.

“I know that millions of people in this country have been suffering, thousands have died, many are angry about what they have seen in the media about my actions,” he said.

“I want to clear up the confusions and misunderstandings where I can.

“In retrospect, I should have made this statement earlier.”

Mr Cummings said allegations he returned to Durham for a second visit after April 14 are “false”.

He said: “I believe in all the circumstances I behaved reasonably and legally.”

He added: “I do not regret what I did” but added that “reasonable people may well disagree”.

Mr Cummings, speaking in Downing Street’s garden, said he was told at around midnight on March 26 by the Prime Minister that he had tested positive for Covid-19.

After discussing the national emergency arrangements, Mr Cummings said he went to Number 10 the following day for a series of meetings.

He received a call from his wife, who was looking after their four-year-old child, who said she felt badly ill, had vomited and felt like she might pass out.

That led to Mr Cummings’ decision to swiftly leave No 10 – actions that were caught on camera in Downing Street.

After a couple of hours his wife felt better and Mr Cummings returned to Downing Street.

But he said that evening he discussed the situation with his wife – including the fact that many in Number 10 had developed coronavirus symptoms.

He was worried that if both he and his wife fell ill there was “nobody in London we could reasonably ask to look after our child and expose themselves to Covid”.

“My tentative conclusion on the Friday evening was this: if we were both unable to look after our child then my sister or nieces can look after him.”

“But, I thought, if I do not develop symptoms and there’s a testing regime in place at work I could return to work if I tested negative. In that situation I could leave my wife and child behind in a safe place – safe in the form of support from family for shopping and emergencies, safe in the sense of being away from our home which had become a target and also safe for everybody else because they were completely isolated on a farm and could not infect anybody.”

He said the nearest other homes are “roughly half a mile away”.

“I did not ask the Prime Minister about this decision. He was ill himself and he had huge problems to deal with. Every day I have to exercise my judgement about things like this and decide what to discuss with him.

“I thought that I would speak to him when the situation clarified over the coming days, including whether I had symptoms and whether there were tests available.

“Arguably this was a mistake and I understand that some will say that I should have spoken to the Prime Minister before deciding what to do.”