Tens of thousands of patients are having their surgery cancelled and hospitals will set up makeshift wards in a dramatic escalation of the NHS’s efforts to avoid the service going into meltdown this winter.

In an unprecedented edict, NHS England has told hospitals to delay operations such as cataract removals and hip and knee replacements until mid-January. The only exceptions to the new policy are cancer operations and also what the NHS called “time-critical procedures” where the surgery has to go ahead to avoid the patient’s condition deteriorating further.

The move, which reflects growing anxiety among NHS bosses about how difficult this winter may prove, is intended to help hospitals cope with an impending influx of patients being admitted as emergencies due to the colder weather.

It has also instructed NHS trusts already experiencing “high levels of operational pressure” this winter to convert clinics and areas usually used for day-case surgery into overflow areas with beds to reduce the risk of running out of space to accommodate patients. The situation threatens a repeat of last winter when some hospitals had to turn gyms and even storage areas into temporary wards.

The edict caused immediate controversy. The Society for Acute Medicine, which represents doctors who look after patients admitted through A&E but who do not need surgery, warned that the ban on operations may have to be extended until the end of February.

“The positive of this is action to relieve pressure on the system. The bad news is that it has happened already, without much actual unexpected stress on the system,” said Dr Nick Scriven, the society’s president.

“We have not yet seen anything out of the ordinary, weather or infection-wise, so my belief is that this stance will need to be extended until at least the end of February,” he added.

Theresa May has made the NHS England chief executive, Simon Stevens, “personally responsible” for how the service performs this winter. He and fellow NHS bosses hope to avoid a repeat of the chaotic scenes experienced in many places last winter, with patients lying on trolleys in corridors waiting for a bed and stuck in ambulances outside A&E units, which led the British Red Cross to declare the situation “a humanitarian crisis”.

Bruce Keogh, the NHS’s national medical director, said: “NHS staff are working flat out to cope with seasonal pressures and ensure patients receive the best possible care. However, given the scale of the challenge, hospitals should be planning for the surge that comes in the new year by freeing up beds and staff where they can to care for our sickest patients.”

Clinics which carry out routine follow-up consultations will instead be turned into “hot clinics” where patients who have been referred to hospital by their GP, for instance because they are not breathing freely, will receive specialist care.

Hospitals are also being advised to undertake more day-case surgery, rather than procedures in which the patient has to stay in to recover, as a way of reducing the pressure on inpatient beds.

Pauline Philip, the NHS’s national director for urgent and emergency care, stressed that the steps were being taken because “the NHS is about to enter into the most challenging part of the year, with spikes in demand likely after the Christmas and New Year breaks”.

Prof Derek Alderson, the president of the Royal College of Surgeons, said it was helpful for patients to have their surgery cancelled well in advance, rather than at 24 hours’ notice, as happened in many places last winter.

But, he added: “Cancelling planned surgery is not a sustainable way of dealing with emergency pressures. Putting aside today’s short-term measure, we urgently need a wider look at how we can protect planned surgery and hospital bed capacity for the future.”

NHS England says the moves are “operational recommendations to hospitals experiencing high levels of operational pressures” and formalise measures already taken by many trusts. “Not everyone has to do everything. It depends how pressurised hospitals are,” a source explained.

Many hospitals are already struggling to meet key waiting time targets this winter, according to the NHS’s most recent figures released on Thursday.

They show, for example, that last week 23 trusts were already 99% full and two trusts 100% full, despite NHS rules which say that hospitals should have no higher than 85% bed occupancy rates in order to maintain patient safety.

Most trusts also failed to treat the required 85% of A&E patients within four hours. Blackpool teaching hospitals trust managed to treat and admit, transfer or discharge just 57.8% of patients within that period, while at East Lancashire hospitals trust it was 64.7% and London North West healthcare trust managed to treat only 65% in that time.

National Voices, a coalition of 160 health and care charities, agreed that the NHS had to prioritise emergency over non-urgent patients in the coming weeks, but said the cancellation of operations reflected “a sorry state of affairs” and that patients would suffer.

“Tens of thousands of people will be affected by delays to their treatment. Operations can be delayed, but the discomfort and pain caused by people’s health conditions cannot be put on hold. Today’s announcement may buy a small amount of time, but it will also build up a considerable backlog of people needing operations,” said Andrew McCracken, its spokesman.

“This is not the first time hospitals have been asked to delay operations, but it needs to be the last. It is not sustainable and cannot become the norm. We still need a proper long-term funding settlement that deals with health and social care together. Until then, we can expect to see services and treatments increasingly rationed.”

Jonathan Ashworth, Labour’s health spokesman, said: “Theresa May’s claims that she has suitably prepared our NHS for the winter season are looking increasingly doubtful. Despite the best efforts of our overstretched staff, numerous trusts are already running at full capacity with no spare beds at all. Cancelled operations will pile more misery on patients this winter.”