Alister Jack, pictured left, the secretary of state for Scotland, said he had not been tested for Covid-19 but had a temperature and a cough.
“In the past 24 hours, I have developed mild symptoms associated with coronavirus. In line with medical guidance, I am self-isolating and working from home,” he said.
His announcement comes after the prime minister and the health secretary, Matt Hancock, confirmed on Friday that they had tested positive for Covid-19. England’s chief medical officer, Prof Chris Whitty, also revealed that he had symptoms.
All three have said they will also continue in their roles while working from home.
Johnson is likely to face further criticism after public health experts on Friday accused him of failing to heed his own advice to the public on how to contain the coronavirus
Jack sat between Johnson and Hancock during prime minister’s questions on Wednesday. The government has recommended everyone keep two metres apart to prevent the spread of the virus.
Dr John Ashton, a former regional director of Public Health England, said on Friday: “The government has been too slow to act on this, and they’ve been slow as individuals. I was surprised to see prime minister questions going ahead this week. It was clearly unnecessary.
“It reinforces the view that lockdown measures taken earlier this week should have been taken sooner, and raises questions about the ability of people in power, including the prime minister, to discipline themselves. They should all have been more careful.”
Parliament has now closed for four weeks after the planned Easter recess was brought forward over concerns about the spread of the virus.
MPs and peers will not return to until 21 April at the earliest, in what may be a limited form.
The Speaker, Lindsay Hoyle, said that “virtual parliament and virtual select committees” could be a possibility as he announced the extended recess on Wednesday evening.
Johnson said in a video message that he would continue to lead efforts to slow the virus’s spread from his flat above No 11 Downing Street.
Concerns are rife that other key government figures might be affected. The chancellor, Rishi Sunak, was with the PM shortly before he tested positive.
The cabinet secretary, Sir Mark Sedwill, was also with Johnson, Hancock and Whitty at a cabinet meeting on Tuesday.
Neither had displayed symptoms by Friday night, so they had not been tested and were not in isolation.