NHS leaders have urged the public to avoid risky activity on Wednesday for fear they may be left helpless and unable to reach A&E during the ambulance strike. The industrial action by staff across England and Wales comes as the ongoing pay dispute between ministers and NHS workers looks poised to descend into an increasingly bitter and disruptive war of attrition that could go on for months. Health chiefs made the remarkable intervention of asking people to avoid getting drunk during the strike, four days before Christmas, as the potential for disruption in transporting people to hospital is so severe. The two bodies representing hospitals and other providers of NHS care in England staged an 11th hour bid to head off Wednesday’s strike by appealing directly to Rishi Sunak for an intervention to end the standoff, warning him that otherwise people “will suffer unnecessarily”. Thousands of patients, including some with serious conditions, will have to make their own way to hospital on Wednesday – often by taxi – because ambulance services are prioritising those with life-threatening conditions, such as cardiac arrest or difficulty breathing. In a sign of how stretched services will be, the Yorkshire ambulance service has told GPs that they should advise patients to get relatives or carers to drive them to A&E, because “the risks of delayed transfer would outweigh the risks of clinically unsupervised transport”. It comes only a day after nurses staged their second strike action of the month. In an unusually strongly worded letter, the NHS Confederation and NHS Providers told the prime minister of the “deep worry among NHS leaders about the level of harm and risk that could occur to patients tomorrow and beyond”. They continued: “We’ve rarely heard such strong and urgent expressions of concern from those running our hospitals, ambulance services and other vital health services. “The fear of NHS leaders is that the risk to patients is only going to get worse with future strikes planned. That is, unless your government is able to reach agreement with the trade unions to bring a swift end to the dispute. “We urge you to do all you can to bring about an agreed solution, otherwise more members of the public will suffer unnecessarily,” they added. However, in an interview with the Daily Mail and an appearance before the Commons liaison committee, Sunak again ruled out any prospect of increasing the £1,400-a-head offer to NHS personnel that he and the health secretary, Steve Barclay, have repeatedly insisted is the most they can afford. He also reiterated that ministers were honouring the advice of the NHS pay review body and would not go beyond it. In remarks that unions saw as a hardening of the government’s position, the prime minister said it was too late to revisit the pay award for 2022-23, which is the nub of the ongoing dispute, instead hinting that next year’s settlement could be more generous if frontline workers called off their nascent campaign of industrial action and accepted the £1,400. Barclay described Wednesday’s strike as “deeply regrettable” and said his “number one priority” was patient safety. “Our ambulance staff are incredibly dedicated to their job and it is deeply regrettable some union members are going ahead with strike action,” he said. “There will be fewer ambulances on the road due to industrial action and the NHS will be prioritising those with life-threatening needs. My message to the public is to take extra care and plan your activity accordingly. You may also want to check up on more vulnerable friends, family and neighbours.” Matthew Taylor, the chief executive of the NHS Confederation, told BBC Radio 4 that, with winter unfolding, more strikes planned and the government implacably opposed to increasing its offer, the NHS and patient care were “entering into a very dangerous time”. “If negotiations do not take place then industrial action will take place. If industrial action takes place, then there will be risk, there will be harm to patients.” In a sign of the intense pressure that ambulance services are already under, eight of England’s 10 regional ambulance services have been forced to declare a “critical incident” an admission they cannot cope with the demand for care and need other NHS services to help relieve the strain. On Wednesday, ambulance services across England and Wales will be much more limited than usual when thousands of members of Unison, Unite and the GMB union withdraw their labour in strikes lasting either 12 or 24 hours. In another setback, talks between Barclay and union leaders over which categories of 999 calls ambulance crews would respond to broke down in acrimony when he again repeated his refusal to discuss the possibility of improving the pay offer. Prof Sir Stephen Powis, NHS England’s national medical director, urged the public to behave in a “sensible” way while ambulance crews are striking by looking in on at-risk neighbours, ensuring they have enough of their own usual medications and not drinking to excess, despite the festive season. He urged anyone worried about their health to call the NHS 111 telephone advice service and to dial 999 only if it was a life-threatening emergency. “But people can also help by taking sensible steps to keep themselves and others safe during this period and not ending up in A&E, whether that is drinking responsibly or checking up on a family member or neighbour who may be particularly vulnerable to make sure they are OK.” Will Quince, a health minister, advised people to not take part in “risky activities” on Wednesday, such as “contact sports”. However, he did not set out which pursuits should be avoided, beyond running on ice, because of the inherent danger. Eluned Morgan, the health minister in Wales, urged people to stock up on first aid kits ahead of Wednesday’s first strike and a planned second day of action next Wednesday by only GMB members and, like Powis and Quince, to refrain from activities that could result in injury. Onay Kasab, Unite’s national lead officer, reflected the fury among the unions when he described the meeting as “entirely pointless”. Sara Gorton, Unison’s head of health, warned that ministers’ intransigence over pay was increasing the possibility that the various health unions at odds with the government – which also includes the Royal College of Nursing, Royal College of Midwives and Chartered Society of Physiotherapists – could start to coordinate their industrial action from early 2023 to increase its impact. In evidence to the Commons health select committee, Rachel Harrison, the GMB’s national secretary, suggested that the government upping its offer from £1,400, which is about 4% for most staff, to 7.5% would be enough for the union to put to its membership to test if it was enough to end the impasse. Six hundred armed forces personnel will help the five ambulance services that operate in London and the north-west, south-east coast and north-east of England, as well as in Yorkshire. They will be paired with paramedics, who they will drive to help injured and seriously unwell patients, but will not provide any clinical care.