Hospitals in England have been ordered to cut back non-urgent operations and cancel outpatient appointments in the run-up to Christmas in preparation for a possible winter crisis, official documents have disclosed.
The move comes as the Royal College of Nursing (RCN) warned of a "drastic shortage" of accident and emergency nurses, with departments across the country "buckling" under the pressure.
A leading emergency doctor said the service could be "poleaxed" in the event of a bad winter flu outbreak.
Details of the planning for a potential crisis like that which saw A&E departments overwhelmed by a flood of emergency admissions in the winter of 2014/15 are disclosed in written evidence to the Commons Health Committee.
In a joint submission, the Department of Health and NHS England said hospital trusts would be required to draw up "specific plans" for winter which would be "assured" by officials nationally.
Measures include reducing the number of "elective" procedures carried out in the period immediately before Christmas to create more "non-elective capacity" and cancelling some outpatient activity.
Trusts will also be required to produce "clear discharge plans" for inpatients prior to the holiday period to provide more beds and patients will be encouraged to make "appropriate choices" on using pharmacies, walk-in centres and GPs to reduce "inappropriate attendance" at A&E.
Dr Cliff Mann, president of the Royal College of Emergency Medicine, told the Daily Telegraph that the service could be in trouble in the event of another difficult winter.
"What is really worrying is that when you look at last winter, the NHS came under very heavy pressures despite mild weather and little flu. All it would take is a bad flu outbreak this winter and we would be poleaxed," he said.
In separate evidence to the committee, the RCN said it was "very concerned" about staffing levels in A&E departments in the face of rising admissions and budgetary constraints.
"There is a drastic shortage of nurses working in A&E departments," it said.
"The RCN is very concerned that A&E departments do not have the appropriate staffing levels, with the right skill mix, in place to deliver safe and appropriate care for patients.
"Across England, the acute sector is buckling under the strain of financial pressures and increased demand for services.
"It is clear that the pressure is affecting the whole system, however, A&E units are often the place where effects are most visible."
A spokesman for NHS England said: "The NHS again proved resilient this winter despite further increase in demand, with fewer trusts reporting serious operational issues and a significant reduction in trolley waits.
"We are already preparing for the upcoming winter with hospitals, GPs, social services and other health professionals coming together to work out the best way of responding in every area of the country."