New data from NHS England reveals that waiting times for treatment are going up, with increasing numbers of people also waiting a year or more.
Earlier this year, NHS England's chief executive, Simon Stevens, acknowledged that p atients will face longer delays for non-urgent operations as the health service focuses on other areas.
The latest NHS England data shows that 409,342 people had waited longer than 18 weeks in August 2017.
This is the highest figure for a single month since almost a decade ago - when 470,983 waited this long in September 2008.
Furthermore, the number of people waiting more than a year for treatment reached 1,729 in August 2017 - the highest number since August 2012 when it was 2,054.
At the end of August this year, there were over 3.8m people in total on the waiting list for treatment - a rise of 3.6% compared to a year earlier.
The percentage of patients treated in under 18 weeks - once a flagship NHS target - is also now at its lowest since March 2011.
In August this year, 89.4% of patients were treated within 18 weeks against a goal of 92%.
The figure has not been this low since March 2011, when it was also 89.4%.
The last time it was lower was in February 2011, when 88.7% of patients started treatment within 18 weeks of referral by their GP.
The new data on A&E performance showed that, in September this year, 89.7% of patients were seen within four hours compared with 90.6% in the same month a year ago.
Cancer treatment times also slipped, with 82.6% of patients starting treatment within 62 days of referral by their doctor for suspected cancer, against a target of 85%.
Half of NHS hospital trusts in England (49%) missed this target.
But there was a slight improvement on patients stuck in hospital despite being medically fit to leave.
In August, patients spent a total of 180,065 extra days in hospital beds waiting to be discharged, compared to 187,851 in the same month the year before.
Ruth Thorlby, assistant director of policy at the Health Foundation, said: " Planning for winter in the NHS has been underway since the summer, but these statistics do not bode well for either patients or staff.
"Hospitals had been set a target to treat or discharge 90% of patients going to A&E within four hours by the end of September, but this has been missed.
"While some progress has been made on reducing the delays in helping people leave hospital safely, it is also well behind the Government's ambitions."
An NHS England spokesman said: "While it's good to see that A&E 4-hour performance year to date has stabilised at 90.2% - ending the annual declines seen in recent years - the whole of the NHS is mobilising for what could be a tough winter.
"Important new action on flu, on delayed hospital discharges, and on more A&E consultants is all being announced today."
Dr Chaand Nagpaul, chairman of the British Medical Association (BMA), said: "These figures point to an NHS under continued pressure.
"Staff across the NHS are gearing up again for the busy winter period and will remember the stress of enduring the worst winter on record last year, with patients facing unacceptable delays for care.
"We don't want to see a repeat of that, this year, which is why it's vital the entire health system is supported and working well - from our GP surgeries, to hospital wards, to social care.
"To achieve this, and ensure the NHS is able to cope with the inevitable spike in demand during the winter period, the Government needs to urgently put in place measures to address the funding, capacity and recruitment issues facing the system as a whole.
"Failure to do so will leave the NHS sleepwalking into another, entirely predictable, winter crisis, with patients and the quality of patient care suffering as a result."