A strike by tens of thousands of nurses starting this Sunday will be cut short after a high court judge ruled that the plans were unlawful. The interim declaration prompted Pat Cullen, the general secretary of the Royal College of Nursing (RCN), to condemn the government for “taking its own nurses to court”. She described it as the darkest day in the long-running pay dispute. Lawyers acting for Steve Barclay, the health and social care secretary, succeeded at the high court on Thursday in arguing that the RCN did not have a mandate for a planned 48-hour strike that was due to end at 8pm on Tuesday 2 May. Mr Justice Linden agreed with the government’s argument that the strike mandate secured by the RCN on 2 November would lose legal standing from 23.59.59 on 1 May. A mandate is valid for six months after a ballot. The government’s success was assured when lawyers acting for the RCN declined to attend to represent the union, in what the judge said was a clear indication that it did not have a case to argue. He said the union should have “grasped the nettle” at an earlier stage and admitted its mistake. The country’s biggest nursing union will now shorten its industrial action so that it begins at the start of the late shift at 8pm on 30 April and ends at midnight on 1 May. The government also asked that the RCN pay its legal costs of £47,885. The judge questioned why the costs were so high and awarded £35,000. Cullen, who joined nurses outside the court in a demonstration on Thursday morning, said she accepted the ruling but claimed it could rally her members to support further strikes. “The full weight of government gave ministers this victory over nursing staff. It is the darkest day of this dispute so far – the government taking its own nurses through the courts in bitterness at their simple expectation of a better pay deal. “Nursing staff will be angered but not crushed by today’s interim order. It may even make them more determined to vote in next month’s reballot for a further six months of action. Nobody wants strikes until Christmas – we should be in the negotiating room, not the courtroom today. Our strike will now finish at midnight on the Monday as we have ensured safe and legal action at all times.” Nurses outside the high court in London carried placards emblazoned with the question “Who takes their heroes to court?”. Government lawyers in the hearing criticised the RCN for not attending in order to argue its points, choosing instead to rely on a witness statement by Cullen. Andrew Burns KC, representing Barclay, described the union as “incompetent in looking at the calendar” and suggested it should have “come clean” over its mistakes. The government lawyers said the RCN, having initially said it would appear to contest the government’s application, had engaged in a “significant U-turn” after a meeting of its governing body, which he claimed had been in a state of paralysis. In a letter to the court, the RCN said it would not be represented in court as it did not want to give credence to Barclay’s legal action and the trade union legislation on which it was based. Linden told the court that Cullen’s witness statement suggested she had accepted the government’s legal position, and he suggested that much of it had been written for a “different audience”. He said it was a concern that the RCN had not attended the hearing of nearly two hours, and that people who did strike on 2 May would not be protected by trades union legislation because it would be unlawful. The union had displayed a “high degree of unreasonableness” in its actions, the judge said. Last year, RCN members voted by 54% to 46% to reject a government offer of a 5% pay rise this year and a cash payment for 2022. They have since rejected an offer of a one-off payment worth between £1,700 and £3,000 for 2022-23 and 5% for 2023-24, with 54% voting against it on a 61% turnout. The union has announced it will seek a second legal mandate to continue its strike action from June to December. While Cullen argued that her members would be enraged by the government’s actions, the court’s judgment also has the potential to undermine unity within the RCN. The biggest healthcare union, Unison, accepted the latest terms offered. The results of ballots of GMB and Unite members will be announced on Friday. The May Day strike still risks causing significant difficulties in the health service. The RCN is refusing to grant the NHS any “derogations” or strike exemptions in key areas of care, such as A&E, intensive care and maternity services. Such exemptions were agreed with the government during the six strikes it held in December, January and February. After the hearing, Barclay called on the RCN to consider derogations to secure patient safety. A reballot of RCN members about further strikes is expected to take place in the next few weeks, with Cullen warning that the industrial action could run all the way until Christmas. Barclay said: “I firmly support the right to take industrial action within the law – but the government could not stand by and let plainly unlawful strike action go ahead. Both the NHS and my team tried to resolve this without resorting to legal action, but unfortunately, following a request from NHS Employers, we took this step with regret to protect nurses by ensuring they are not asked to take part in an unlawful strike. “We welcome the decision of the high court that the Royal College of Nursing’s planned strike on 2 May is illegal. The government wants to continue working constructively with the Royal College of Nursing, as was the case when we agreed the pay offer that was endorsed by their leadership. We now call on them to do the right thing by patients and agree derogations for their strike action on 30 May and 1 April.” Meanwhile, GP leaders have warned ministers that family doctors in England may go on strike in protest at the government imposing its latest employment contact with the NHS on them. The British Medical Association’s GPs committee voted on Thursday to begin entering into a dispute with the Department of Health and Social Care over its decision to force upon GPs a contract they claim includes “disastrous” changes that would endanger patients’ safety. The GPs committee’s acting chair, Dr Kieran Sharrock, said it would hold an indicative ballot, to establish support for GPs going on strike, unless ministers reopened negotiations about the contract. Physiotherapists in England have accepted the government’s improved pay offer for 2022-23 and this year. Of the 61% of the Chartered Society of Physiotherapy’s 20,000 members in England, 65% voted in a ballot to accept the deal while 35% rejected it. It is the second NHS union after Unison to accept the one-off payment averaging about £2,000 for last year and a 5% rise for this year, which ministers offered last month after a series of strikes over the winter.