A charity has raised concerns about the rising numbers of patients waiting for key diagnostics tests which detect cancer and other diseases.
Macmillan Cancer Support said it is "worrying" that the number of patients waiting more than the recommended six weeks for key tests has reached a six-year high.
Latest NHS England figures show that 16,981 patients were waiting six weeks or more for 15 diagnostic tests including MRI and CT scans, audiology assessments or cardiac echos - or 2.2% of all of the patients waiting for such tests.
The figure is the highest it has been for six years - in April 2008 just 2,904 patients were waiting for these checks.
Ciaran Devane, chief executive at Macmillan Cancer Support, said: "It is extremely worrying that the proportion of people who face delays in receiving vital tests which can diagnose cancer has doubled since this time last year, from 1.1% to 2.2%.
"Only two weeks ago we heard that more people are waiting longer to start treatment and now more people are waiting longer just to get diagnosed.
"Once again, we see that cancer care in this country isn't fixed. The NHS is under strain and cancer risks being overlooked and not given the focus it needs.
"Each individual hospital has a responsibility to meet these targets, or they risk putting a patient's best chance of survival at risk. However, this Government and the next also need to take responsibility.
"Macmillan Cancer Support is urging all political parties to make cancer a top priority at the upcoming general election."
Labour's shadow health secretary Andy Burnham said: " Patients are waiting longer for crucial tests - causing stress and real anguish for worried families. Two weeks ago, the NHS missed the cancer treatment target for the first time ever and these delays have clearly played a part in that.
"All the progress made on cancer care in the last decade is now at risk."
An NHS England spokeswoman said: "Timeliness of diagnosis and treatment is what patients expect and is essential to providing high-quality care.
"The vast majority of patients get their tests promptly with most patients waiting less than three weeks from referral, despite the number of tests rising by almost 56,000 when compared to the same period last year."
Yesterday it was announced that extra funds are to be ploughed into the NHS to help keep waiting times down.
NHS organisations in England have been invited to apply for a share of a £250 million fund to try to reduce the number of patients waiting for elective surgeries.
There are 250,000 more patients who are waiting for pre-planned surgery than the same time last year, figures show.
Health officials said that the rise in waits are linked to the ageing population, with more referrals than ever being sent from GPs to hospital consultants. In May 2010, 1.4 million people were being referred for elective operations every month, this has now risen to 1.5 million each month.
The one-off cash injection aims to tackle a rise in demand for elective care, the Department of Health said.
NHS trusts have been invited to apply for a share of the money which will be made available in July and August.