Day surgery theatre nurses are to strike at two central London hospitals after bosses extended their shifts by an hour, Unite announced on Monday.
The union said 50 workers are due to walk out from Guy’s and St Thomas’ on June 27 and July 2, after the end of their shift time was extended from 8pm to 9pm.
It warned further strike action will be scheduled if the dispute is not resolved.
Nurses say they have already been chronically overworked due to shifts initially being extended from 7pm to 8pm - with some staff members having to work on Saturdays to support extra theatre lists.
Unite general secretary Sharon Graham said: “Guy’s and St Thomas’ theatre nurses were already running on fumes. They were working beyond their shifts to ensure patients were cared for properly.
“Our members understand the pressure the NHS is under but working staff until they break is not the answer.
“Guy’s and St Thomas’ leadership must find another way. Unite is dedicated to protecting the jobs, pay and conditions and the workers at Guy’s and St Thomas’ have the union’s total support throughout this dispute.”
Around 2.6 million patient contacts visit Guy’s and St Thomas’ in central London every year, making it one of the UK's busiest NHS trusts.
Staff at the hospitals have warned that an increase in shift time is compromising patient safety.
One theatre nurse said: “Staff in the day surgery units at Guy’s and St Thomas's hospitals are striking because they are tired of having their concerns over burn out and patient safety repeatedly ignored by managers.
“The situation has now reached crisis point, with nurses feeling like they have no option but to strike to protect themselves and their patients.”
A spokesperson for Guy’s and St Thomas’ NHS Foundation Trust said: “We are disappointed that Unite are continuing with these strikes while constructive talks are ongoing. We would urge them to call off this action so we can continue making progress on improving the shift patterns for our highly valued and important theatre nurses.
“We are working closely with colleagues to plan for the impact of this strike, and any changes to patient care will be communicated directly to patients and via our usual public channels as appropriate.”