More than four million people on the total NHS waiting lists are facing nine-month waits for a diagnosis, with delays twice as long as they were before the pandemic, new analysis shows.
Sir Bruce Keogh, a former NHS medical director, said patients were facing "intolerable" waits amid warnings that thousands of people with undiagnosed cancer are among those "left in limbo".
The Policy Exchange report found that four-fifths of the 5.3 million people on the total NHS lists have not had a decision taken about whether their symptoms require admission to hospital.
Average waiting times for this group of 4.2 million have reached 37 weeks – up from 22 before the pandemic. Experts said patients with deadly cancers and other fatal conditions are among those facing such delays.
While the NHS attempts to speed up diagnosis and treatment of patients when cancer is suspected, around 90,000 cases a year are already found from those who were not put on this pathway.
Cancer referrals have fallen during the pandemic
In a preface to the report, Sir Bruce, who retired as NHS medical director in 2018, said the public expected better than the "intolerable waiting lists" they were having to endure.
"While people gathered in the streets to applaud the NHS as it grappled with the biggest healthcare crisis in living memory, many families were quietly worried about when they would get less urgent treatment," he wrote. "Some people sat on evolving symptoms with fear or uncertainty in the absence of a diagnosis, while others lived with pain and discomfort awaiting procedures postponed for an indeterminate period.
"Whilst a tolerant British public played their part in reducing demand for non-Covid services, that tolerance must be repaid or it will wane with the pandemic, as families pay a very personal price for delays in diagnosis and treatment."
The report called for new NHS targets including waiting no longer than eight weeks for a diagnosis. It also urged a £1.3 billion investment in diagnostics.
It highlighted a lack of data published by the NHS, which does not publish data directly measuring waiting times for diagnosis. The authors said the waiting times for those awaiting a decision to admit to hospital, either for in or outpatient treatment, were the closest measure published and showed average times almost doubling.
Stephen Dorrell, a former Health Secretary said: "In an age when Amazon can send a message which predicts to within two hours the time of delivery of a parcel sent from the Far East to your home, it is humiliating that the NHS is unable to offer any meaningful guidance on when it will be able to treat your painful or life limiting condition.
"Millions of patients are being kept in the dark about when they will be treated and how long they must wait – we cannot let this continue. After Covid, as waiting lists grow, the NHS needs a transparency revolution."
Robert Ede, the head of health and social care policy at Policy Exchange and the lead author of the report, said too many patients were being "left in limbo" with no information about how long they might have to wait to even find out what was wrong with them.
He added: "There has been a lot of focus on those waiting a long time for treatment, but the figure that should be keeping the new NHS chief executive up at night is 4.2 million – the number of people with a routine referral still awaiting a decision from a specialist.
"This is an enormous clinical risk. A proportion of these patients will have a cancer and other urgent hidden conditions."
Prof Neil Mortensen, the president of the Royal College of Surgeons of England, said the state of the waiting lists was "politically unacceptable". He backed calls in the report for the creation of centralised "surgical hubs" working around the clock, saying patients would be willing to travel further to be seen sooner.