The NHS is at “breaking point” as fewer hospital beds mean delayed admissions and cancelled operations, the British Medical Association says.
The BMA report says the number of overnight beds in English hospitals fell by a fifth between 2006/7 and 2015/16.
It found 14.8% of patients spent more than four hours waiting for a bed after going to A&E, in November 2016.
In the first week of January, almost three-quarters of trusts had a bed occupancy rate of over 95% on at least one day.
Labour said the report was a “wake-up call which Theresa May must not ignore”.
The Liberal Democrats warned the situation was becoming “intolerable”.
Mark Porter, chairman of the BMA which represents doctors in the UK, said: “The UK already has the second lowest number of hospital beds per head in Europe per head and these figures paint an even bleaker picture of an NHS that is at breaking point.
“High bed occupancy is a symptom of wider pressure and demand on an overstretched and underfunded system.
“It causes delays in admissions, operations being cancelled and patients being unfairly and sometimes repeatedly let down.
“The delays that vulnerable patients are facing, particularly those with mental health issues, have almost become the norm and this is unacceptable.”
He continued: “In the long term we need politicians to take their heads of out the sand and provide a sustainable solution to the funding and capacity challenges that are overwhelming the health service.”
Department of Health officials disputed some of the report’s key findings.
They insisted changes in the way data were recorded meant historic figures could not be compared to the current situation.