The number of people on NHS waiting lists in England is at a new record high as health service leaders warn the system is buckling under pressure.

Data from NHS England shows 5.8 million people were waiting to start treatment at the end of September – the highest number since records began in August 2007.

The number of people having to wait more than 52 weeks to start treatment stood at 300,566 in September, up from 292,138 in the previous month and more than double the number waiting a year earlier, in September 2020, which was 139,545.

The number of people admitted for routine treatment in hospitals, however, is returning to pre-pandemic levels.

It came as the NHS Confederation warned that hospitals are facing intolerable pressure even before the full impact of winter has been felt, while ambulance trusts are failing to get to 999 calls on time, leaving some people with no care for hours.

All ambulance trusts in England are currently on a high level of alert and are under significant strain.

They are missing targets for responding to calls, with the longest average response times since current monthly records began in August 2017.

The latest data for October shows that the average response time for ambulances dealing with the most urgent Category 1 incidents – defined as life-threatening illnesses or injuries such as a cardiac arrest – was nine minutes and 20 seconds, compared with a target of seven minutes.

Ambulances in England also took an average of 53 minutes and 54 seconds last month to respond to Category 2 calls, such as burns, epilepsy and strokes, up from 45 minutes and 30 seconds in September, and missing the 18-minute target.

Response times for urgent calls – such as late stages of labour, non-severe burns and diabetes – averaged three hours, nine minutes and 58 seconds.

This is up from two hours, 35 minutes and 45 seconds in September, and again is the longest average since current records began.

NHS England argued that 999 services had their busiest ever month in October as staff answered a record 1,012,143 calls.

Ambulance staff responded to more than 82,000 life-threatening callouts, an increase of more than 20,000 on the previous high for October in 2019 (61,561), it said.

It also said major A&Es treated more than 1.4 million people during October – the highest ever for the month and third highest of all time.

The data showed a record 7,059 people had to wait more than 12 hours at A&Es from a decision to admit to actually being admitted – the highest for any calendar month since records began in August 2010.

Some 121,000 people waited at least four hours from the decision to admit to admission – the highest monthly total on record.

Professor Stephen Powis, NHS national medical director said: “With the highest number of 999 calls ever answered for a single month, the busiest October on record for major A&E, and the rollout of boosters as part of the successful NHS vaccination programme, there is no doubt pressure on the health service remains incredibly high.

“But, despite high demand, NHS staff are going above and beyond to see more patients and deliver millions more tests, checks, treatments and operations.

“Increasing numbers are coming forward for treatment and this is expected to go up, but it remains really important people do not delay seeking help from the NHS if they feel unwell.”

Earlier, Matthew Taylor, chief executive of the NHS Confederation, said a survey of more than 450 leaders across all parts of the health service found nine out of 10 said the situation they now face is “unsustainable” and patient care is being compromised.

Tim Gardner, senior fellow at the Health Foundation, said of the new data: “With waiting lists at an all-time high, millions of patients and staff are feeling the impact of a health system struggling to cope with demand.

‘The Government has said that the NHS is under ‘sustainable pressure’, but it would be extraordinary to look at what’s happening in the NHS right now and claim that it is sustainable.

“There are multiple factors which are already impacting patient care – delays to cancer treatment and routine operations, record high waits for ambulances and in A&E, high demand for GP appointments and an overstretched workforce exhausted by the pandemic – all of which are reflected in today’s figures.

“That we are facing pressures this significant before we have reached the peak of winter is concerning, particularly as cases of seasonal viruses and rising staff absences are likely to add further pressure.”

Lengthening delays and cancellations are becoming a source of frustration for patients in constituencies across the length and breadth of the country

The new NHS data shows nearly 370,000 patients in England had been waiting more than six weeks for a key diagnostic test in September.

A total of 369,207 patients were waiting for one of 15 standard tests, including an MRI scan, non-obstetric ultrasound or gastroscopy.

The equivalent number waiting for more than six weeks in September 2020 was 419,841, while pre-pandemic in September 2019 there were 38,802.

The NHS England figures also showed 231,421 urgent cancer referrals were made by GPs in England in September, up 15% from the 201,013 reported in September last year.

The equivalent figure for September 2019, a non-pandemic year, was 195,196.

Commenting on the long waits for surgery, Fiona Myint, vice president of the Royal College of Surgeons of England, said: “Lengthening delays and cancellations are becoming a source of frustration for patients in constituencies across the length and breadth of the country.

“Their lives are effectively on hold, waiting for planned surgery on hips and knees.

“Surgical procedures to treat aneurysms and prevent heart attacks are also affected.”