The Public and Commercial Services (PCS) union, which represents the workers, is seeking a pay rise and improvements to conditions in areas such as holiday entitlement, and, more widely, is trying to persuade the Labour government to bring staff currently employed by an outsourcing company into official roles.
As well as the direct dispute on pay and conditions, the PCS is pressuring ministers to act on previous pledges to gradually end the outsourcing of jobs such as cleaning, catering and security in government departments.
The month-long strike will include workers at No 10 and the Cabinet Office, as well as the Department for Energy Security and Net Zero, the Department for Education, the Department for Science, Innovation and Technology, and the Department for Business and Trade.
The strike, scheduled to last from 24 February to 25 March, is an extension of a wider dispute that has already taken place in a series of government departments, but will now be extended to No 10 and the Cabinet Office.
A PCS official said the current contracts with PCS and other outsourcing firms such as G4S and OCS run out in three years, and that talks about bringing people on to civil service contracts needed to start soon.
