Hundreds of civil servants in two government departments are to go on strike in protest at plans to privatise their work.
Human resources, finance and other back office staff at the Department for Work and Pensions and Department for the Environment, Food and Rural Affairs will walk out for 24 hours on Friday.
The Public and Commercial Services union is campaigning against plans to sell off a range of government department support functions, warning that some work will be transferred abroad.
General secretary Mark Serwotka said: "From day one, ministers have pushed for this work to go overseas, putting jobs at risk and threatening the security of sensitive financial information.
"We will not stand by and watch while yet another piece of the civil service is parcelled up and handed to a private company to make a profit."
The strike will affect offices in Blackpool, Cardiff, Leeds, Newcastle, Sheffield and York.
A Cabinet Office spokesman said: "The Civil Service is moving to be faster, smaller and more unified and sharing services is a central part of this. The Next Generation Shared Services Strategy sets out a new model to share HR, procurement, finance and payroll functions with five centres instead of the current eight in order to deliver more efficient and cost-effective services.
"The process of selecting a private sector joint venture partner for the second of the two independent centres has commenced and we have consulted with staff and unions throughout, and continue to do so. An announcement will be made in due course."