Prime Minister Boris Johnson has been admitted to the Intensive Care Unit as his coronavirus symptoms worsen.
Foreign & Commonwealth Secretary Dominic Raab is deputising for Mr Johnson.
A number 10 spokesperson said: “Since Sunday evening, the Prime Minister has been under the care of doctors at St Thomas’ Hospital, in London, after being admitted with persistent symptoms of coronavirus.
“Over the course of this afternoon, the condition of the Prime Minister has worsened and, on the advice of his medical team, he has been moved to the Intensive Care Unit at the hospital.
“The PM has asked Foreign Secretary Dominic Raab, who is the First Secretary of State, to deputise for him where necessary.
“The PM is receiving excellent care, and thanks all NHS staff for their hard work and dedication.”
Mr Johnson was admitted to hospital on Sunday evening for what Downing Street described as “precautionary tests.”
His condition worsened on Monday afternoon, with the decision being made to transfer him to ICU at around 7pm that evening.
The Prime Minister is conscious although key functions of his office have been handed over to his Deputy, Dominic Raab.