More than 15 per cent of cancer patients under the Chiltern Clinical Commissioning Group waited at least two months to start treatment following referral by their GP.

During the 2017-18 financial year, 683 cancer patients were referred to hospital urgently by their doctors, but 108 did not start their treatment within 62 days, according to NHS figures.

The government has a target of 85 per cent of all referrals to have treatment start within two months.

This is to allow for the minority of patients who choose to delay their course of treatment, which may be chemotherapy, surgery or radiation therapy.

In Chiltern CCG 84.2 per cent of patients began treatment within two months of an urgent GP referral, slightly below the NHS target.

In Aylesbury Vale CCG 81.9 per cent of patients began treatment within two months.

That's roughly the same as 2016-17, when 83.8 per cent of patients started treatment two months after referral in Chiltern and 82.2 per cent in Aylesbury.

Across England more than three quarters of all CCGs are running below the operational target.

The best record is in South Cheshire CCG where 93 per cent of cancer patients started treatment within two months. But in Thurrock CCG, Essex, it was just 59 per cent.

Dr Jeanette Dickson, vice president of clinical oncology at the Royal College of Radiologists, said that while the figures "are a cause for concern" they are a slightly crude measure for judging cancer diagnosis.

"In an ideal world we would want it to be 100 per cent," Dr Dickson said.

However, she explained getting from the GP to treatment is a complicated process requiring many different appointments and staff.

"There is currently a shortage of radiologists (doctors who give X-rays), and to a lesser extent oncologists (doctors specialising in cancer).

"Some people will choose to delay the treatment beyond the two month time period."

Dr Dickson said the time periods required for treating different forms of cancer are vastly different.

"With your average male prostate cancer patient, you will do nothing but examine and watch for ten years.

"However, with tongue cancer or aggressive lung cancer you need to start treatment within three weeks otherwise it's likely the patient will have less chance surviving."

Across England the percentage of patients starting treatment within two months has dropped from 87.1 per cent in 2012-2013, to 82.1 per cent last year.

The operational target hasn't been hit since 2013.

Emlyn Samuel, head of policy development at Cancer Research UK, called on the Government to recruit more staff.

He said: "While most patients start their cancer treatment within two months of an urgent referral, the target of 85 per cent of patients is still being missed.

"We know that local hospitals make every effort to meet this target, but shortages in NHS diagnostic staff put services under severe pressure.

"Waiting for tests or to start treatment can be an anxious time for patients, so the Government must ensure that there are more staff to deliver the tests and treatment that people need."

An NHS England spokeswoman said: "Cancer survival is now at an all-time high, but as part of our push for earlier diagnosis the NHS is deliberately putting itself under pressure by significantly increasing the number of people referred for quick cancer checks.

"So last year over 1.9 million people were urgently referred for suspected cancer by their GP - half a million more than just three years ago."