Downing Street insisted it was just a precautionary measure but Johnson’s admission on a Sunday evening comes after days of rumours that his condition has been worsening.
A Downing Street spokesperson said: “On the advice of his doctor, the prime minister has tonight been admitted to hospital for tests. This is a precautionary step, as the prime minister continues to have persistent symptoms of coronavirus 10 days after testing positive for the virus.”
Johnson is reported to be in an NHS hospital in London where he will stay for “as long as needed.”
It is understood Johnson remains in charge of the government, although Dominic Raab, the foreign secretary and first secretary of state, is poised to take charge if he should worsen.
Raab, who is the designated minister to take over if the PM is incapacitated, will chair the 9.15am Monday meeting of the government’s C-19 committee, which leads the response to the pandemic.
Johnson had been hoping to leave quarantine on Friday after seven days of self isolation but his persistent temperature meant he had to remain inside his flat at No 11 Downing Street, the report said
The Guardian was told last week that Johnson was more seriously ill than either he or his officials were prepared to admit, and that he was being seen by doctors who were concerned about his breathing, the report said.
But Downing Street flatly denied that the prime minister’s health had seriously deteriorated, and insisted there were no plans at that point for him to be admitted to hospital, the report said.
Earlier on Sunday, Matt Hancock was asked just how ill the prime minister was. The health secretary told Sophy Ridge on Sunday: “He’s OK. I’ve been talking to him every day, several times a day… he’s very much got his hand on the tiller. But he’s still got a temperature.”
He added: “He’s working away inside Downing Street. He’s in good spirits.”
Johnson’s partner, Carrie Symonds, who is pregnant, revealed on Saturday that she had also been suffering from the virus but is recovering.
Keir Starmer, the new Labour leader, was among a string of MPs to tweet their best wishes to Johnson. “Wishing the prime minister well and a speedy recovery,” he wrote.
Jeremy Hunt, the former health secretary and Johnson’s main rival for the Conservative leadership last year, tweeted: “Thoughts with Boris Johnson this evening. Whatever political persuasion the whole country is united in wanting our PM to get fit and well as soon as possible.”
(Update: Boris Johnson was reportedly treated with oxygen after being admitted to hospital, Metro reported. The PM spent the night at St Thomas’ Hospital in central London, and will likely undergo a barrage of tests, including checking his oxygen levels, white blood cell count, liver and kidney function and an electrocardiogram, before he is released.)