Rishi Sunak’s “increasingly intransigent” and “belligerent” stance on medics’ pay is blocking the path to ending the industrial action in the NHS, leaving no option but to strike until the next general election, one of Britain’s top doctors has warned. Speaking to the Guardian on Friday after junior doctors launched a fifth round of industrial action, Prof Philip Banfield, the chair of the British Medical Association (BMA) council, said the union was standing firm and that doctors would continue to hold stoppages until they received a “credible offer”. The latest round of strike action by junior doctors in England will run until 7am on Tuesday next week. BMA consultants are already lining up to strike for two days this month and two days in September, and Banfield said doctors were ready to strike “into and beyond the next general election”. He accused the prime minister of being “unwilling to talk” and failing to make “any significant steps” towards ending the strikes. The future of the NHS was at stake, he said, and it had been “chronically run down” on the government’s watch. “We are now in the sixth month of strike action, involving tens of thousands of doctors; from the very junior to the most experienced, all have stood on picket lines,” Banfield said. “The prime minister and health secretary have grown increasingly intransigent, belligerent and unwilling to talk about how we reach agreed settlements to end the juniors’ and consultants’ disputes. “The government has, without a shadow of doubt, failed to make any significant steps towards ending the strikes. “For the sake of patients we will continue to push for resolution, but the future of an NHS that has been chronically run down on this government’s watch is at stake, and doctors will continue to advocate for patients into and beyond the next general election. Any prime minister should be in no doubt that doctors in England are determined to continue with industrial action until and unless a credible offer is made.” Banfield’s intervention came after a health chief said industrial action since December last year had cost the NHS about £1bn. Sir Julian Hartley, the chief executive of NHS Providers, said trusts were having to “pay premium rates to consultants” to cover junior doctors while they were on picket lines. Hartley said the strikes were expected to lead to 1 million appointments being cancelled and rearranged by the time the round of action finished next week. The health secretary, Steve Barclay, claimed on Friday that the strike action by doctors “serves only to harm patients” and put “further pressure” on their colleagues. Writing for the Daily Mail, he said: “I want to have a grown-up conversation about how to fix the legitimate frustrations these doctors face, and work together to improve their working lives. “Striking is not going to help anyone achieve that and, ultimately, it is patients that have to bear the brunt of walkouts.” The Department of Health and Social Care said the pay rise offered to junior doctors – a 6% hike and an additional consolidated £1,250 increase, which the government described as an “average increase of around 8.8%” – was “fair and reasonable” and “above what most in the public and private sectors are receiving”. Banfield said in response: “Throughout, our messages to this government have never wavered: make a credible offer to restore the value of pay and make our pay review body truly independent as it was set up to be. “Our door has remained open and we have asked time and time again for the health minister and then the prime minster to come to the negotiating table, to work with us directly, or through Acas, to make a credible offer which could bring an end to the strikes.”