The NHS is now on track for a record number of cancer patients not receiving treatment on time - described as a "depressing milestone" by charities.
One in five patients wait too long for cancer treatment, with more than 73,000 waiting more than two months in the last four years, new data shows.
Some 20,137 patients in England have had to wait longer than two months to start treatment following an urgent referral to hospital by their GP, figures for 2015/16 to date show.
In the whole of the previous year, 21,407 patients were not treated within the two-month target, while more than 55,000 have not been treated on time since 2012.
Experts said huge financial pressures were to blame for the rising numbers.
The target is for 85% of patients to be seen within two months of urgent referral.
This has now been missed for almost two years and was last hit annually in 2013/14.
The latest data, published by NHS England, shows 82.3% of patients were seen within the target for 2015/16 to date, while 83.4% were seen in the previous year.
Figures for 2015/16 to date show that 113,901 patients have been referred, with 93,764 treated on time and 20,137 waiting longer.
In 2014/15, 128,642 were referred, of whom 107,235 received a first treatment on time and 21,407 waited longer.
In 2013/14, 123,543 were referred under the target, with 106,104 treated within the target and 17,439 waiting longer, while in 2012/13, 116,528 patients were referred, with 101,632 treated within the target and 14,896 waiting longer.
While the number of patients needing urgent referrals for cancer treatment has risen steadily in recent years, experts said this was not the reason why patients were forced to wait.
John Appleby, from the King's Fund think tank, said: "Whilst there is a weak association between increased hospital activity (ie, more patients being treated) and longer waiting times, it is more likely this deteriorating performance is symptomatic of the huge financial pressures on NHS trusts."
Emlyn Samuel, Cancer Research UK's senior policy manager, said: "Failure to meet this target means that in recent years tens of thousands of patients have had to wait longer than two months to start cancer treatment.
"These targets exist to ensure swift diagnosis and access to cancer treatment, which is vital if we're to give patients the best chance of a cure and are serious about having survival rates as good as anywhere in the world.
"The recent cancer strategy sets out the ambition to diagnose and treat cancer at an earlier stage while improving patient experience, so action is needed now to turn around this unacceptable situation for patients."
Dr Fran Woodard, executive director of policy and impact at Macmillan Cancer Support, said the charity was "bitterly disappointed" the cancer target was being missed.
"More than half of trusts (58%) are currently failing people - clearly not enough has been done to make sure that cancer patients across the country experience swift referrals for treatments.
"Last year, the cancer strategy for England was published, which was an acknowledgement that more needs to be done to support people affected by cancer.
"Yet here we are at this depressing milestone for waiting times, without a firm commitment to implementing what was recommended.
"Waiting a long time to be diagnosed and to start treatment is the last thing people need at what is already an incredibly tough time.
"We must see urgent improvements if the NHS has any hope of handling increasing pressures and giving people affected by cancer the best support possible to cope with this debilitating disease."
Nigel Edwards, chief executive of the Nuffield Trust, said: "Today's drop in performance is yet another example of the great pressure the entire health service is facing."
An NHS England spokesman said: "The NHS is helping more people survive cancer than ever before and we've met and exceeded seven of the eight cancer waiting time standards.
"Swift diagnosis is key and these figures show that more people than ever are seeing a specialist within two weeks of visiting their GP.
"The Independent Cancer Taskforce has made a number of recommendations to support earlier diagnosis and better treatment, and we are working with partners across the health system to take these forward as quickly as possible."