The target time period for those referred for urgent treatment after being diagnosed with suspected cancer has been breached for the first time since it was introduced.
NHS guidelines stipulate that 85% of patients should wait a maximum of 62 days to begin their first definitive treatment following an urgent referral for suspected cancer from their GP.
But figures released today show that this slipped to 84.4% during the period January to March, down from 85.8% during the last quarter.
National clinical director for Cancer for NHS England, Sean Duffy, said work must be done to make sure standards are met.
"It is vital cancer patients are diagnosed and treated quickly so they have the best possible chance of recovery," he said.
"Latest figures show nationally the NHS has met and exceeded seven out of eight cancer waiting time standards. But there is variation in meeting the challenging standards, and national performance against one of the targets has dipped.
"CCG commissioners are working together with local providers where the standard is not being met to identify the issues to ensure patients are treated in a timely way."
Other figures released by NHS England on cancer waiting times showed the number of people seen by a specialist within two weeks of an urgent GP referral for suspected cancer has also dropped from 95.6% to 95%, while 93.9% of people urgently referred for breast symptoms (where cancer was not initially suspected) were seen within two weeks compared to 95.5% previously - just within the target of 93%.
In total, 60,425 patients with exhibited breast symptoms where cancer was not initially suspected were seen in the first three months of this year after being urgently referred. Of these, 93.9% were seen within 14 days, compared to 95.5% in the previous quarter and 95.7% in the first three months of last year.
In all cancers, patients should experience a maximum wait of one month (31 days) between receiving their diagnosis and the start of first definitive treatment, with the operational standard being 96%.
While this target was met, the number of people beginning their first definitive treatment within the period fell from 98.3% at the end of last year to 98% in the first three months of this year.
Levels also decreased in those diagnosed with breast cancer (from 99.2% to 98.9%), lung cancers (from 98.9% to 98.6%), lower gastrointestinal cancers (98.5% to 98.3%), urological cancers (96.4% to 96.1%) and skin cancers (down from 98.1% to 97.8%).
The failure in the 62-day wait from urgent GP referral to first definitive treatment is the first breach of any cancer waiting time since the introduction of the current operational standard in 2009.
Further figures relating to this target indicate that 96.6% of people treated for breast cancers met the guideline compared to 97% in the last three months of last year, while it also dropped among those treated for lower gastrointestinal cancers ( 76.8% compared to 78.7% previously) and urological cancers (excluding testicular cancer) which fell from 81.5% to 78.7%.
Only in those with lung cancers did figures improve, from 77.8% in the final quarter of last year to 78.2% this year, and skin cancers which went up from 95.8% to 96.2%.
Results for waiting times for second or subsequent treatment show that 96.8% of people underwent surgery within 31 days, down from 97% the previous quarter, while when the treatment was an anti-cancer drug regimen 99.6% began receiving it, compared to 99.8% previously.
In cases where the patient was given radiotherapy, 97.1% began treatment within 31 days, a drop from 97.2% in the last three months of last year.
Mike Hobday, director of policy and research at Macmillan Cancer Support, said the figures were worrying.
He said: "This is the first breach of any cancer waiting time in England since 2009 and is a clear warning sign that the NHS is under huge strain.
"The UK already has some of the worst cancer survival rates in Europe. More patients are now facing delays, which means more patients are facing anxiety for longer and more lives are being put at risk. We're very worried that the coordination of cancer care is getting worse and that cancer is being overlooked in the new NHS.
"The number of cancer patients is set to increase from two to three million by the end of the next Government in 2020, and we can't afford to see more and more people waiting longer.
"Ahead of next year's general election, Macmillan Cancer Support is urging all political parties to commit to delivering cancer outcomes that match the best in Europe and to make cancer a top priority for the next government."