More than 100,000 people with suspected cancer are not being seen within the appropriate timeframe every year, an investigation has found.
Figures gathered by the Guardian show that last year 101,140 patients in England with suspect symptoms were not seen by a specialist within 14 days.
A patient with suspected cancer is urgently referred to an oncology specialist by their GP and the vast majority are expected to be seen within a fortnight.
But the analysis of NHS-wide performance data carried out by Cancer Research UK and shared with the newspaper show that many patients are being forced to wait longer than this timeframe.
Professor Peter Johnson, Cancer Research UK's chief clinician, told the newspaper: "These figures are alarming. The number of people for whom these targets are being missed is a real source of concern.
"Delay creates additional anxiety for people. That matters for individual patients affected in a precise way because they have a prolonged period of uncertainty. Do I have cancer or do I not? And if I do have cancer, will it be curable?
"In some cases delays may even mean the chance to give curative treatment may be lost.
"Delays mean that there will be some people whose cancer gets worse while they wait for the result (of a test). I'm pretty angry about that.
"This all reflects a system that's failing to meet the needs of people with cancer or suspected cancer."
A Department of Health spokesman told the newspaper: "Cancer survival rates have never been higher and just this week the NHS announced a new £130 million investment to kick-start the upgrade of radiotherapy equipment and transform cancer treatment across England.
"The reality is the NHS is seeing over 90% more patients with suspected cancer within two weeks - that's over 800,000 more people - and treating nearly 50,000 more patients following a GP referral compared to 2010."