eThere will be no extra NHS funding without reform, Sir Keir Starmer says, as he promised to draw up a new 10-year plan for the health service.
The pledge came after a damning report warned the NHS in England was in a "critical condition".
The prime minister said the new plan, expected to be published in the spring, would be the "the biggest re-imagining of the NHS" since it was formed.
He set out three key areas for reform - the transition to a digital NHS, moving more care from hospitals to communities, and focusing efforts on prevention over sickness.
But the Conservatives said the government needed to turn "rhetoric to action" after scrapping its plans to reform social care and build new hospitals.
The report, external was the result of a nine-week review by the independent peer and NHS surgeon Lord Darzi.
He was asked by Labour, shortly after the election, to identify the failings in the health service, but his remit did not stretch to coming up with solutions.
His findings present a stark picture of a service which he says is in "serious trouble" with declining productivity, "ballooning" waits and "awful" emergency services that put patients at risk.