The Prime Minister’s chief adviser, Dominic Cummings, is self-isolating after developing coronavirus-like symptoms, Number 10 has confirmed.

Mr Cummings becomes the latest member of the Downing Street inner circle to either be diagnosed with Covid-19 or be forced to self-isolate as a result of noticing symptoms associated with the deadly virus.

Boris Johnson, Health Secretary Matt Hancock and the UK’s Brexit negotiator, David Frost, have all been struck down with coronavirus, while chief medical officer Professor Chris Whitty has quarantined himself after noticing symptoms.

Scotland Secretary Alister Jack, who sat between Conservative Party leader Mr Johnson and Mr Hancock at Prime Minister’s Questions on Wednesday, confirmed at the weekend that he has a cough and a temperature – tell-tale signs of coronavirus – and would remain at home, making him the third Cabinet minister to shut themselves away.

Mr Cummings, the mastermind behind Vote Leave’s messaging at the EU referendum, was last seen running out of Number 10 shortly after Mr Johnson posted a video message on Friday announcing he had tested positive.

The Prime Minister’s official spokesman said the 48-year-old noticed symptoms of Covid-19 over the course of the weekend and had decided to self-isolate.

Asked whether Mr Cummings had been tested for coronavirus, the spokesman added: “I wouldn’t expect that to be the case.”

He will continue to stay in contact with the Downing Street team while in isolation, a Number 10 source told the PA news agency.

Father-of-one Mr Cummings has proved a controversial figure, both before and after his appointment by Mr Johnson.

Downing Street last week denied suggestions that the PM’s top aide had been prepared to let the elderly die to protect the economy during the UK outbreak of coronavirus.

Cummings Covid-19
Dominic Cummings, wearing tracksuit bottoms, arrives in Downing Street the day after Boris Johnson put the UK in lockdown to help curb the spread of the coronavirus (PA Video/PA)

Number 10 branded as “highly defamatory” a Sunday Times report which claimed that Mr Cummings supported so-called “herd immunity” even if it meant older people died.

The PM’s spokesman said Mr Johnson was continuing to lead on the virus response while holed up in Number 11, where he occupies the upstairs flat.

“He is chairing the daily meetings using video conferencing facilities, he is working from the Chancellor’s office, he has been able to do everything he needs to do to lead the coronavirus response,” said the spokesman.

As of Sunday, there were 19,522 positive cases in the UK and 1,228 of those admitted to hospital with Covid-19 had died.