Thousands of patients who have had strokes, heart attacks or broken bones will have to get themselves to A&E on Wednesday when ambulance staff strike over pay, NHS bosses have warned. The disruption is expected to last for up to three days, with crews not reaching some patients who called 999 on Wednesday until Thursday or Friday. Hospital bosses have told the Guardian they fear Wednesday’s strike by ambulance personnel across England and Wales will entail a “huge risk of harm” to patients, including older people left lying on a floor for days with a broken hip getting hypothermia and dying. Only category one patients – those at immediate risk of dying, for example because they have stopped breathing – will be sent an ambulance during the 24-hour stoppage, with everyone else having to make other arrangements. Union leaders say they have no choice but to take the drastic action, imploring ministers to come to the negotiating table and improve pay for paramedics amid soaring inflation. It comes as up to 100,000 members of the Royal College of Nursing (RCN) will strike again on Tuesday over pay and concerns about patient safety, after a day of industrial action last week. NHS England is under fire from GPs for not warning the public to avoid taking part in risky pursuits on Wednesday and to look out for vulnerable relatives and friends. The campaign group GP Survival – to which 9,300 family doctors belong – also said in a letter to Amanda Pritchard, NHS England’s chief executive, that it should also have already issued “practical advice to the public on how to move and transport injured and acutely unwell patients to emergency departments”. North West ambulance service (NWAS) gave a foretaste of the chaos that is likely to envelop ambulance services generally this week in a letter to GPs, NHS trusts and NHS111 telephone advice services across the 4,500 sq mile swathe of England it covers. It warned that patients would have to get themselves to hospital from GP surgeries, walk-in centres and care homes, unless they were having a cardiac arrest or facing another threat to their life. Mothers-to-be will have to do the same unless they are having an “obstetric emergency”, such as going into premature labour. The NHS in Greater Manchester has even advised GPs across the region to pay for taxis to take patients to hospital who cannot get an ambulance, and offered to reimburse them for doing so. Health unions have blamed the situation on the government’s refusal to talk to them about improving the £1,400-a-head offer it made to most NHS personnel in the summer. Speaking before the ambulance stoppage and Tuesday’s second strike by nurses, Christina McAnea, the general secretary of Unison, said: “There’d be no strikes at all if ministers would only talk to unions and improve NHS pay.” Steve Barclay, the health secretary, should “throw all his energy into preventing the strikes from going ahead this week and preventing any escalation of action in the new year”, McAnea said. It was “inevitable” that strikes would become more disruptive to NHS services and patients from next month unless Barclay changed tack, she stressed. Barclay and Rishi Sunak are under growing pressure from within Conservative ranks to ditch their hardline stance and start negotiating to avoid what may become a winter-long series of strikes. Referring to the likely impact of this week’s ambulance strike, one acute hospital chief executive said: “Most category one calls are supposed to be life-threatening so should be prioritised. But for category two and below it’s far less certain that people will get any kind of response, other than telephone advice. “We are likely to see people with suspected strokes or heart attacks being asked to make their own way to hospital. A fit younger adult with a broken leg wouldn’t get an ambulance in these circumstances and it’s unlikely that an elderly person who has fallen at home would either.” A second trust boss said it was “realistic” to worry that a frail older person who lived alone could fall and break their hip on Wednesday, but not get an ambulance for 24 or even 48 hours – and develop hypothermia from lying on a cold floor before ultimately dying of pneumonia. “Patients with confusion could be left wandering the streets, frail elderly with breathing problems or a broken wrist or shoulder and even some people who’ve been in a road traffic accident – it’s likely that even they won’t get an ambulance and will have to make their own way or wait for an ambulance, though they could be waiting until Thursday or even Friday for that,” they said. In its letter to Pritchard, GP Survival said it was “astounded at the dereliction of duty by NHS England, which has always been quick to remind GPs of their responsibilities but appears to ignore its own role in patient safety and education, instead leaving the public apprehensive and confused”. The letter, organised by the GP Survival chair, Dr John Hughes, also warns that patients who suffer acute illness, accidents and falls on Wednesday will find themselves in a position of “double jeopardy” because ambulance services will be “severely denuded” while alternative arrangements being put in place to get people to hospital, such as army vehicles, will not be staffed by trained paramedics. Members of Unison, Unite and the GMB working in ambulance services will strike for 24 hours on Wednesday in 10 of the 11 regional ambulance services in England and Wales. The GMB intends to mount a second stoppage across both countries on Wednesday 28 December.