Officials from NHS England say there were 110,100 emergency admissions to hospital in the first week of December - one of the highest numbers since records began more than a decade ago.
More than 435,000 patients attended A&E - 30,000 more than the average - leading to a further deterioration in performance against the key treatment target which saw 91.8 per cent of people treated within four hours, well below the 95 per cent standard.
The worsening position came despite no real signs of a flu crisis or major problems due to diarrhoea and vomiting.
Ministers have already delivered an emergency injection of £700 million into NHS services to deal with winter pressures.
NHS bosses say they are tightly monitoring the position to spot problems early ahead of a major review of urgent care due to report soon.
British Medical Association chairman Mark Porter said: “Patients should be treated on the basis of clinical need rather than an arbitrary target, but these figures point to a system cracking under extreme pressure, leading to unacceptable delays in care.
“While the NHS is used to seeing a spike in demand during winter months, this year it’s experienced a spring, summer and autumn crisis as well, leaving no spare capacity in hospitals as we hit winter.
“This is not just a crisis in emergency care – bed shortages and high numbers of patients inappropriately in hospital beds are now major stress factors on the system, leading to unacceptable delays in treating and discharging patients.
“Outside of hospitals, GP surgeries are struggling to cope with unprecedented levels of demand.
“Frontline staff are working flat-out but the system can’t cope with the sheer number of patients coming through the door.
“So far there has been a total failure by government to come up with a meaningful plan to deal with this – funding announced recently to tackle winter pressures is simply recycled money, taken from other overstretched services.
“To alleviate pressure on the system we need to ensure people are better supported to self-care where appropriate, and that they get the right advice first time round on where to seek treatment so as to avoid unnecessary trips to A&E.
“An effective out-of-hours telephone service is crucial to this, yet NHS 111 is still falling short of the mark because it isn’t clinician-led.
“We also need a system-wide approach which addresses the flow of patients across the NHS.
“There is no getting away from the fact that the NHS needs more investment to ensure there are enough staff and resources to meet rising demand, and part of this means taking urgent action to address the high number of staff vacancies in emergency medicine as well as general practice.”
Former Bradford GP Dame Barbara Hakin, national director of commissioning operations for NHS England, said: “Unsurprisingly, this level of demand continues to put extra pressure on our hospitals but the NHS remains resilient and is pulling out all the stops, with local hospitals, ambulances, GPs, home health services and local councils all working hard to open extra beds and seven day services using the extra winter funding that has been made available.”