The Labour leader is preparing to accuse the prime minister of losing his authority and being “too preoccupied defending his rule-breaking” to meet the huge challenges faced by the health service.
Mr Johnson is fighting to save his premiership after he admitted attending a “bring your own booze” event in May 2020, with further reports of leaving drinks at No 10 and Whitehall during the pandemic.
On Saturday, in a speech at the Fabian Society conference, Sir Keir is due to set out his “personal crusade” for NHS reform, accusing the Conservatives allowing the health service to fall into a “critical” condition.
“Rather than concentrating on getting through the pandemic and bringing down waiting lists, this self-indulgent Tory party is instead having a fight about a leader who they should have known from the start is not fit for office,” he is expected to say.
The Labour leader will add: “We are witnessing the broken spectacle of a prime minister mired in deceit and deception, unable to lead.”
On his “personal crusade” for the NHS, Keir Starmer is expected to say: “I spent a lot of time as a child visiting my mum in hospital. I have never forgotten the care my mum received, the respect with which she was treated. I want that level of care for everyone.”
The opposition leader will use his Fabian speech to describe his vision of a “contract for better health” under a Labour government – with a promise to shift health care towards prevention to reflect Britain’s ageing society, according to party officials.
Sir Keir will also promise that the next Labour government would treat mental health “as seriously as physical health”.
At its party conference last September, Labour pledged to recruit more than 8,500 mental health professionals to support a million more people every year, with a commitment to provide mental health support in under a month.
The Labour leader again called on Mr Johnson to resign after Downing Street apologised to Buckingham Palace over leaving parties held in No 10 the day before the Duke of Edinburgh’s funeral last April.
“This shows just how seriously Boris Johnson has degraded the office of prime minister,” said Sir Keir. “An apology isn’t the only thing the prime minister should be offering the palace today. Boris Johnson should do the decent thing and resign.”
It comes as the latest YouGov poll gave Labour a 11-point lead over the Conservatives, the biggest recorded by the company since 2013.
A separate Savanta poll for The Independent found that 70 per cent of voters want Mr Johnson to resign – a record high figure.