The NHS is facing a day of massive disruption next month when nurses and ambulance staff in England and Wales stage an unprecedented joint strike over pay. Health service bosses said the coordinated walkouts were “a huge concern” and Monday 6 February “could be the biggest day of industrial action the NHS has ever seen”. One senior NHS leader said hospitals would “grind to a halt” as doctors and nurses from other departments are redeployed to provide emergency cover in strike-hit A&E units. It will be the first time that nurses and ambulance workers, including paramedics and call handlers, have refused to work at the same time. The escalation of the dispute puts pressure on Rishi Sunak to find a way to deal with the health unions. On Wednesday the prime minister and Keir Starmer again traded blows about the state of the NHS. Between 30,000 and 40,000 nurses in England and Wales were already due to stage the fifth one-day stoppage of their campaign on 6 February. On Wednesday the GMB union announced it would call more than 10,000 paramedics, call handlers and other ambulance service staff out on the same date, as one of four more days of its own industrial action. A senior official at an NHS trust in England said hospitals would be forced to cancel non-urgent operations scheduled for that day, as part of a concerted effort to help emergency departments cope with the absence of many of their staff. “Coordinated strike action is certainly a real concern if it increases the risk of being able to maintain safe staffing in critical areas, particularly in A&E,” they said. Nurses will strike at 55 trusts on Thursday, the second consecutive day of action. Taken together with the impact of two days of action in December at 44 trusts , hospitals will have been forced to cancel about 10,000 operations and 50,000 outpatient appointments, the NHS Confederation said. Ministers continue to refuse to improve the below-inflation pay offers already on the table or, in the case of NHS staff and teachers, even to hold detailed talks with their representatives. At prime minister’s questions on Wednesday, Starmer cited long waits for an ambulance as proof of the “lethal chaos” preventing the health service from providing quick treatment. The Labour leader asked Sunak to apologise, and highlighted the case of a 26-year-old woman with cancer whom he referred to only as Stephanie, who died while waiting for an ambulance in Plymouth. Sunak declined to do so and instead accused the opposition leader of “playing political games when it comes to people’s healthcare”. Saffron Cordery, the interim chief executive of NHS Providers, reflected health chiefs’ acute anxiety over the impact of the double walkout on 6 February. “Trusts have been warning for months that coordinated strikes were a possibility if the government and unions failed to reach an early agreement on this year’s pay award. The prospect of ambulance workers and nurses striking on the same day is a huge concern. It could be the biggest day of industrial action the NHS has ever seen,” she said. “We need ministers to get round the table with the unions urgently to deal with the key issue of pay for this financial year, otherwise there is no light at the end of the tunnel.” The NHS Confederation issued a similar plea. “Our message to the government is … do all you can to bring an end to this damaging dispute”, said its chief executive, Matthew Taylor. Some health unions are confused about the government’s approach to increasing the £1,400-a-head award it has imposed on NHS staff for 2022-23. Steve Barclay, the health secretary, said on Wednesday that retrospective pay hikes for NHS staff for 2022-23 were unaffordable. Those comments appear to contradict briefings from government sources and unions after the last round of talks with Barclay, held on 9 January, when he agreed to take unions’ concerns about pay to the Treasury. Whitehall sources have conceded over the past week that there is now an acceptance within government that a one-off cost of living payment or a pay rise for 2023-24 backdated to 1 January will be the only way forward. But Jeremy Hunt, the chancellor, is understood to have told Barclay there will be no new money for the pay deal, which will have to come out of the existing NHS budget. Meanwhile, talks between teaching unions and the education secretary, Gillian Keegan, to try to avert a planned series of strikes in schools broke down after just over an hour on Wednesday, with no progress made towards finding a resolution. Mary Bousted, the joint general secretary of the National Education Union (NEU), said the meeting was “constructive” and the secretary of state had been keen to talk about issues affecting teachers such as workload and recruitment and retention. But there was no discussion about an improved pay deal for either this year or next. “I’m happy to talk about all these other issues, but we’re not talking about things that will resolve the pay dispute,” Bousted said. Her members are due to hold stoppages on and after 1 February. Geoff Barton, the general secretary of the Association of School and College Leaders, said unresolved issues included “the inadequacy of the pay award” of 5% for this academic year, which he said was “well below inflation”. The government’s determination to cap teachers’ pay rise in 2023-24 at just 2% was also key, he said. A minister admitted to MPs on Wednesday that rail strikes had cost the UK economy more than £1bn, and it would have cost less to settle the long-running dispute with unions over pay and conditions months ago. However, the rail minister Huw Merriman said the need for changes to working practices made the standoff necessary, as he told the Commons transport select committee the government had not “torpedoed” a deal nor “interfered in a negative manner”.