The action follows a dispute over Doncaster and Bassetlaw Teaching Hospitals' (DBTH) proposal for ICU nurses at Bassetlaw to take part in an eight-week rotation each year to Doncaster Royal Infirmary, as part of a 12-month cycle, to maintain essential skills, competencies and experience.

Unite says the trust's proposal would not guarantee increased exposure to level 3 patients.

The union says the nurses fear the transfers are one more step towards Bassetlaw hospital losing its ICU permanently through ‘decommissioning by stealth'. They would also face overly long commutes before and after 13-hour shifts, with the risk of exhaustion putting themselves and patients at risk.

In addition, Unite claims that the trust is threatening to dismiss the nurses from their current contracts and rehire them on new ones on 12 December.

The nurses began action short of strike action through a ban on working on any ward or unit other than Bassetlaw ICU on 13 November and took two days of strike action in late November. They will strike again from 15-19 December.

Sharon Graham, Unite general secretary, said: ‘The trust's abhorrent fire and rehire threats have only made the nurses more determined to fight against this blatant attempt to run down Bassetlaw's ICU. They have Unite's 100% support in standing up for themselves and patients.'

The union says it is considering legal challenges to Doncaster & Bassetlaw Teaching Hospitals NHS Foundation Trust should it proceed with its plans.

Unite regional officer Chris Rawlinson said: ‘Unite offered the trust a cost-neutral plan that would give nurses more level 3 experience. Its rejection of the plan shows the real aim: the decommissioning by stealth of Bassetlaw's ICU.

‘Our members don't want to strike, but they can't accept proposals that undermine patient care and force unreasonable commute times on top of 13-hour shifts.'

In response, Karen Jessop, chief nurse at DBTH, said: ‘Our priority is patient safety, and that means ensuring our highly skilled ICU nurses maintain the level of competency critically ill patients rightly expect. Bassetlaw Hospital sees fewer very sick patients, and a short-term rotation with Doncaster is the safest and most effective way to keep those specialist skills up-to-date.

‘We have worked closely with colleagues and unions, and we believe our offer is practical, supportive, and focused on enabling our teams to continue delivering the safest, highest-quality care.'