Sir Keir Starmer will warn the NHS must "reform or die" after a report into the state of the health service found it to be in "critical condition".
Health secretary Wes Streeting ordered the independent investigation just days after Labour took office.
The Prime Minister is set to announce the results of that report on Thursday, which also says the nation's health has significantly deteriorated over the past 15 years.
Sir Keir will lay the blame directly at the door of the Conservatives, saying: "The 2010s were a lost decade for our NHS... which left the NHS unable to be there for patients today, and totally unprepared for the challenges and opportunities of tomorrow.
"Our NHS went into the pandemic in a much more fragile state. We had higher bed occupancy rates, fewer doctors, fewer nurses and fewer beds than most other high income health systems in the world.
"And let's be clear about what caused that... a 'scorched earth' approach to health reform, the effects of which are still felt to this day."
The Labour leader will also offer his party's own solutions to the problem with a 10-year plan that promises to have "the fingerprints of NHS staff and patients all over it".
In response, Shadow health secretary Victoria Atkins said: "We Conservatives recognise that investment has to be married with reform. This is why we brought forward long-term plans for productivity, tech, 'Pharmacy First', virtual wards, attracting pharmaceutical research and training and retaining staff. We did this whilst boosting investment in the NHS in real terms every single year.
"The Labour government will be judged on its actions. It has stopped new hospitals from being built, scrapped our social care reforms and taken money from pensioners to fund unsustainable pay rises with no gains in productivity. They need to move from rhetoric to action."