Just 88.9% of patients were seen within four hours in A&E departments in November, the lowest figure since February, as the arrival of winter put further pressure on the NHS.
NHS England said there were 512,962 emergency admissions last month, 4.8% higher than the same month last year.
Of these, 48,339 patients waited more than four hours, with 109 waiting over 12 hours.
The operational standard for A&E waiting times is that 95% of patients should be admitted, transferred or discharged within four hours of arrival at an A&E department. This has not been met since July 2015.
Dr Nick Scriven, president of the Society for Acute Medicine, said frontline staff across the UK have been reporting their hospitals are "imploding" and there is "carnage on the ground" as the cold weather bites.
"When we talk about the NHS at the moment, all we can say and see is pressure, pressure and more pressure, the system is on a knife-edge," he said.
"Some hospitals are already cancelling planned surgery and that is something patients will face increasingly over the winter months."
Weekly NHS data showed there were 11,900 ambulance delays of more than 30 minutes in the past week, up from 10,200 the previous week.
Of these, 2,340 were delays of more than 60 minutes, up from 1,840.
There was also a sharp rise in the number of bed closures due to norovirus, or diarrhoea and vomiting, increasing from an average of 664 beds to 1,123 per day.
Two flu-related deaths brings the total to six so far this winter.
Labour's shadow health secretary Jonathan Ashworth said: "Last week's cold snap demonstrated once again the crisis facing our NHS this winter and Government inaction will only make the challenge facing the NHS that much harder.
"Patients will be deeply concerned that despite the heroic efforts of our brilliant NHS staff, there was a shocking 27% increase in the number of patients stuck for over an hour in the back of an ambulance in just one week.
"Despite the pressures which all frontline NHS staff were warning of, the winter fund announced in the budget has still not been fully allocated to struggling trusts. Patients expect ministers to urgently get a grip."
An NHS England spokesman said: "A&E four-hour performance in November is now better than the same time last year, despite an extra 85,000 more patients being successfully treated in under four hours.
"There has also been progress on reducing delayed transfers of care, with more than 1,000 beds freed up compared with last winter.
"Combined with additional winter funding being allocated to trusts, this means the originally planned 2,500 extra bed availability will be on stream over the coming winter period.
"The public can continue to play their part by ensuring they have their flu jab and by using local pharmacies and NHS 111 for medical advice, alongside other services."
Janet Davies, general secretary of the Royal College of Nursing (RCN), said: "All this points to overflowing hospitals unable to discharge patients quickly enough.
"The Government shouldn't shrug today's figures off as yet more statistics, behind every one is a person waiting too long, often in pain and discomfort and at their lowest ebb."