England’s National Health Service, one of the country’s most revered institutions, is in “critical” condition, according to a government-commissioned report that cited long waits for treatment, crumbling hospitals, mental health patients in “vermin-infested cells” and far fewer M.R.I. scanners than in comparable countries.

The hard-hitting review, published late on Wednesday, was commissioned by Britain’s new prime minister, Keir Starmer, after he won the general election. The dire state of the N.H.S. was a key reason many people voted for his Labour Party in July, according to polls.

But the report underscores the scale of the challenge the government faces to revive a health care system that is in a spiral of decline after years of underinvestment and administrative meddling and is still suffering the aftershocks of the pandemic.

Mr. Starmer said in comments his office released on Wednesday that he was working on a 10-year plan that could amount to the “biggest reimagining of our N.H.S.” since its creation in 1948.

The report, written by Ara Darzi, a surgeon and member of the House of Lords, said that during the 2010s, when a Conservative-led government embarked on a stringent austerity program, the N.H.S. was “starved of capital,” leading it to fall behind other countries in terms of investing in diagnostic equipment, technology and buildings.

His findings will not surprise Britons, whose satisfaction in the health service is “at its lowest ever,” the report said, having peaked in 2009. Still, even Professor Darzi, who has spent three decades in the N.H.S., said that he was “shocked” by what he discovered and laid the blame for the problems on successive Conservative governments that held power for 14 years.