The NHS has been warned it needs 10,000 additional hospital beds this winter in order to keep patients safe.
The British Medical Association (BMA) said the approaching winter period "could be the worst on record" for emergency departments, which are predicted to see an increase in patients and longer waiting times.
New analysis from the doctors' union suggests between January and March next year, the total number of emergency hospital admissions will rise to more than 1.6 million from 1.5 million this year.
The number of A&E patients waiting over four hours at major emergency departments could increase to over one million, the BMA said, while the number of patients waiting for beds for four hours of more will rise from 226,000 to 238,000. In the worst-case scenario it could rise to more than 300,000.
Meanwhile, its analysis of bed occupancy found that last winter occupancy peaked at 95 per cent.
But the BMA said previous guidance has suggested occupancy should not exceed 85 per cent or it could affect quality of care.
It has been suggested that if occupancy is above 92 cent, the deterioration in emergency care standards begins to accelerate, the BMA added.
It said that high bed occupancy rates lead to issues across all hospital departments and is often a factor in the decision to cancel planned operations.
It can also delay patients moving from the emergency department to a ward, doctors added.
To bring bed occupancy down to the recommended minimum safe limit of 92 per cent, the NHS in England will need to use 5,000 "escalation beds" opened last winter, and will need an additional 5,000 general and acute beds.
Dr Rob Harwood, chairman of the body's consultant committee, said: "The NHS is facing an all-year crisis that is leaving patients in an intolerable situation.
"This winter could be the worst on record for frontline emergency care departments, with a BMA analysis suggesting hundreds of thousands of patients will be left either waiting to see a doctor for an assessment or stranded in cramped corridors on a hospital trolley waiting for a hospital bed to become available.
"A key part of this problem is the lack of available beds within the NHS system.
"Last winter saw incredibly high levels of bed occupancy, well above recommended limits, and despite thousands of escalation beds being put into action temporarily.
"At this level patients will struggle to get the attention and care they need."
Commenting on the analysis, Labour's shadow health secretary Jonathan Ashworth said: "This report is the latest from a long line of medical staff clearly already deeply concerned about the encroaching winter crisis.
"The UK already has the second lowest number of hospital beds per head to comparable nations in Europe and consistently high bed occupancy is compromising patient safety."
Additional reporting by PA
