The Government is taking legal action over a planned 48-hour strike by nurses in the long-running dispute over pay.
Royal College of Nursing (RCN) members working in the NHS in England at workplaces with a strike mandate are preparing to take industrial action from 8 pm or the start of the night shift on April 30 until 8 pm or the start of the night shift on May 2.
NHS employers wrote to the Health and Social Care Secretary Steve Barclay asking him to check the legality of the action because the strike mandate runs out in early May.
Mr Barclay said: "Following a request from NHS Employers, I have regretfully provided notice of my intent to pursue legal action to ask the courts to declare the Royal College of Nursing's upcoming strike action planned for April 30 to May 2 to be unlawful.
"The Government firmly believes in the right to strike but it is vital that any industrial action is lawful and I have no choice but to take action," the Health Secretary said. "Strike action with no national exemptions agreed, including for emergency and cancer care, will also put patient safety at risk.
"This legal action also seeks to protect nurses who could otherwise be asked to take part in unlawful activity that could in turn put their professional registration at risk and would breach the requirements set out in the nursing code of conduct."
'Nakedly Political': RCN
"This legal action also seeks to protect nurses who could otherwise be asked to take part in unlawful activity that could in turn put their professional registration at risk and would breach the requirements set out in the nursing code of conduct."
RCN General-Secretary Pat Cullen said: "This is nakedly political. Nurses will not be gagged in this way by a bullying Government.
"We are clear that court arguments should only relate to 2nd May and not the 30th April and 1st May," she added. "The Government is now desperate to silence nurses rather than address this properly. We want to be in the negotiating room, not the courtroom."
Speaking to BBC Radio 4’s "Today" programme, Ms Cullen said: "We have managed 6 months of industrial action and we have done that in the most safe and effective way.
"We will certainly not put our members at risk, we certainly won’t put our patients at risk," she said.
Ms Cullen urged ministers to "calm this down" and resume negotiations.
She added that the union had been planning with NHS England and other service leaders for the potential industrial action next month, including ensuring there are protocols for escalation to ensure patient safety is not put at risk.
However, she went on: "If the court finds against us, then we will absolutely work within the parameters of the law.