No 10 no longer describes coronavirus symptoms as mild and does not deny he had oxygen

Boris Johnson is still in hospital suffering from coronavirus and had a “comfortable night” but No 10 has dropped the description of his symptoms as mild.

As the prime minister continues to be observed by doctors, Downing Street said it was too early to say whether he would be staying for another night and did not deny that he had been given oxygen treatment.

The prime minister’s official spokesman said he was in St Thomas’ hospital in south London and was in “good spirits”, while continuing to work on his red box of government papers.

Asked whether Johnson had pneumonia, the spokesman said any change in his condition would be communicated to the public. He still has a cough and a temperature, more than 11 days after first reporting symptoms.

No 10 insisted it had been “transparent throughout” Johnson’s illness, despite having described the prime minister’s symptoms as mild right up until his hospital admission. Johnson himself only admitted to still having a temperature, not a cough, in his video message on Friday morning. No 10 has now changed its description of his symptoms to “persistent”.

Two Tory ministers – Nadine Dorries and James Duddridge – have suggested Johnson needs to rest.

However, No 10 said he was taking advice from his doctors on whether it was safe for him to continue working and was still in touch with No 10 officials from his hospital bed.

Earlier, Robert Jenrick, the communities secretary, insisted Johnson was fit enough to lead the country from his hospital bed after he was admitted with persistent coronavirus symptoms.

Quick guide UK lockdown: what are the coronavirus restrictions? Show Hide What do the restrictions involve? People in the UK will only be allowed to leave their home for the following purposes: Shopping for basic necessities, as infrequently as possible

One form of exercise a day – for example a run, walk, or cycle – alone or with members of your household

Any medical need, to provide care or to help a vulnerable person

Travelling to and from work, but only where this is absolutely necessary and cannot be done from home Police will have the powers to enforce the rules, including through fines and dispersing gatherings. To ensure compliance with the instruction to stay at home, the government will: Close all shops selling non-essential goods, including clothing and electronic stores and other premises including libraries, playgrounds and outdoor gyms, and places of worship

Stop all gatherings of more than two people in public – excluding people you live with

Stop all social events, including weddings, baptisms and other ceremonies, but excluding funerals Parks will remain open for exercise, but gatherings will be dispersed.

Johnson was admitted on Sunday evening with a high fever on the advice of his doctor, with Downing Street saying he was undergoing routine tests. He was kept in overnight.

Most coronavirus patients stay in hospital for more than a week. However, Jenrick told BBC Breakfast: “We all hope and expect that he can get back to No 10 very soon.”

If his condition worsens, Dominic Raab, the foreign secretary and first secretary of state, is the designated minister to take charge. Raab chaired a Monday morning meeting of the government’s C-19 committee, which is leading the response to the pandemic. However, Tuesday’s cabinet meeting has been cancelled.

The pound fell against the dollar and euro overnight on Monday as foreign exchange markets took fright at the possibility of Johnson being out of action. The prime minister had been hoping to leave quarantine on Friday but his persistent temperature meant he had to remain inside his flat at No 11 Downing Street.

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.

But Downing Street flatly denied the prime minister’s health had seriously deteriorated, and insisted there were no plans at that point for him to be admitted to hospital.

Asked if it was time for colleagues in the cabinet and civil service to tell Johnson to rest, Jenrick told BBC Radio 4’s Today programme: “He has worked phenomenally hard, as have many people across the country. This has been a uniquely intense period and I know for him personally it will be very frustrating that he has had to go to hospital to have these tests.

“He will want to be back in No 10 leading from the front, which is his way. But he remains in charge of the government; he will be updated regularly in hospital, as he has been as he’s self-isolating.”

On Sunday, Matt Hancock was asked just how ill the prime minister was. The health secretary told Sophy Ridge on Sky News: “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.”

Johnson’s partner, Carrie Symonds, who is pregnant, revealed on Saturday that she had also contracted the virus but was recovering.

While No 10 did not say what tests Johnson would have in hospital, experts said they would be likely to focus on assessing how the prime minister’s lungs, heart and other organs were responding to the virus.

“Doctors will be monitoring important vital signs such as oxygen saturations,” said Dr Rupert Beale, who heads the cell biology of infection laboratory at the Francis Crick Institute in London.

“They will also check blood tests to see what the immune response to the virus looks like, and to assess liver and kidney function. They will perform an electrocardiogram to check the heart. More sophisticated tests may include a CT scan of the chest to get an accurate picture of the lungs.”

With Johnson in hospital, the ministers involved in the government’s coronavirus response will be looking ahead to next weekend, which is the point at which it will have to extend or end the lockdown.

Jenrick signalled the lockdown was unlikely to be lifted at the end of the week, saying some of the most challenging weeks were probably still to come. As communities secretary, he said the government “desperately” did not want to shut parks but it could happen if people continued to congregate for picnics.

Critics of the government are concerned that ministers have not identified a way out of the lockdown, with doubts about its ability to scale up testing for live cases and the efficacy of new antibody tests to find out whether people have had the virus.

The former prime minister Tony Blair called for a senior minister to “take charge of testing, and nothing else, with people with business experience of how you ramp up industrial scale production”.

He said it was not the right choice for an epidemiologist to be in charge of this effort, after the government put Prof John Newton of Public Health England in charge.

“Unless you are able to get mass testing at scale, with speed, I don’t see how you can get a way out of this lockdown and I am terrified by the economic damage we are doing with every week this lockdown continues,” Blair told the Today programme.

“This damage is enormous … If it goes on for a long time then it doesn’t just affect the economy per se, it also affects the ability to operate your healthcare service effectively.”

His comments echo the calls of the former health secretary Jeremy Hunt, who has for more than a week advocated a return to mass community testing to suppress virus hotspots where they arise.