Thousands of staff at east London NHS trusts will take part in strikes next month.
Unite the Union said more than 2,800 of its members at four trusts will walk out across a number of days in September.
These include Barts Health NHS Trust, which runs hospitals such as The Royal London and Newham, and Barking, Havering and Redbridge University Hospitals NHS Trust, which oversees Queen's Hospital in Romford and King George Hospital in Goodmayes.
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East London NHS Foundation Trust and Guy's and St Thomas’ NHS Foundation Trust will also be affected.
The union said the action comes amidst a "staffing crisis".
The strikes, involving nurses, pathologists, cleaners, caterers, porters and ancillary staff, will be held on various days between September 13 and 22.
Reporting by PA.
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