Dominic Raab does not have full prime ministerial responsibility while deputising for Boris Johnson, with no power to hire and fire or take major decisions without cabinet agreement.
The foreign secretary was given the duty of standing in for Johnson “where appropriate” following the prime minister’s admission to intensive care on Monday night, but this is understood to relate mainly to the government’s coronavirus response, with no specific instructions to extend his reach into other areas.
If Raab himself were to become incapacitated, the next in command would be Rishi Sunak, the chancellor.
Ministers refused to say on Tuesday whether Raab now has custody of the UK’s nuclear codes as a “matter of national security” but No 10 made clear that he would only be able to authorise military action if it were the collective decision of cabinet.
Raab is also not charged with taking over Johnson’s weekly audience with the Queen, which has been cancelled while the prime minister remains incapacitated.
The foreign secretary has not yet spoken to Johnson since his admission to intensive care, with their last conversation occurring on Saturday – before Johnson went to hospital.
No 10 was reticent about whether the prime minister was still communicating with his deputy or officials, and said there was no information to provide on whether he can sit up, talk or stay in touch while in intensive care.
Speaking at the daily No 10 press conference, Raab said he had “clear instructions” from Johnson about what needed to be done, and the principle of collective decision-making by cabinet was no different from usual.
But he avoided a question on whether he would be able to authorise a change in the direction of strategy if there is disagreement within the cabinet.
With Johnson in hospital for a second day, Raab chaired the government’s daily coronavirus “war cabinet” meeting on Tuesday morning, where the chief advisers gave updates on the national situation. The meeting was also attended by Michael Gove and Sunak.
However, some MPs and experts have raised concerns that Raab’s responsibilities need to be set out more clearly, particularly if Johnson remains unable to work.
Tobias Ellwood, the Tory former defence minister and current chair of the defence select committee, said: “It is important to have 100% clarity as to where responsibility for UK national security decisions now lies. We must anticipate adversaries attempting to exploit any perceived weakness.”
Robert Hazell, professor of government and the constitution at University College London, said if Johnson is unwell for an extended period “it will be the cabinet who will discuss this and decide what to do”.
They could install a caretaker prime minister followed by a leadership election, he said.
Despite No 10’s assertion that Johnson has not given hiring and firing powers to Raab, Hazell said it would fall to him if necessary.
“Ultimately, ministers are appointed and dismissed by the Queen and the Queen normally acts on the advice of the person who is the primary constitutional adviser, who is the prime minister. If the prime minister is incapacitated, she turns to the person who the prime minister has nominated, which is Dominic Raab.”
He also thought Raab would have the technical power to go to the Queen to request a minister be dismissed if they had behaved so heinously the only option was a sacking.
On whether Raab could take the UK to war when the prime minister is still in hospital, he said it would in theory be possible.
“Suppose that the UK, or more likely one of its dependent territories, came under attack, suppose we had a rerun of the Falklands for example, I do not feel that he would say to Argentina: ‘This is very unsporting of you to do this while the prime minister is incapacitated.’
“He would ask Mark Sedwill [the cabinet secretary] to convene a special security council so the government is not disabled and take the decision.”
Hazell said “the cabinet manual is silent” on what happens if the PM is unable to return to his job because of illness.
He said it would be likely that the “cabinet would have to decide who should be his successor and the cabinet would advise the Queen to make the appointment”.
“In order to earn the confidence of the public, it could be a two-stage process, with a caretaker prime minister appointed ahead of a leadership election which could take three months,” he said, adding that his hunch is that the caretaker would be someone who is not intending on running for leader.
A sudden succession process was not unusual in the past but has not been triggered since the Victorian era.
Seven British prime ministers have died in office, including William Pitt the Younger in 1806 and Spencer Perceval who was assassinated in 1812. The Australian prime minister Harold Holt drowned in 1967. While there were no written rules on succession, ultimately the parliament decided the succession process.