Civil servants are to vote on whether to hold a strike ballot over pay following years of wage restraint.
A decision will be taken at the annual conference of the Public and Commercial Services union (PCS) today, which said the pay of civil servants has fallen by 9% in real terms since 2010.
The union said it has been told by the Government it has only budgeted for a 1% pay rise this year, well below the rate of inflation.
PCS general secretary Mark Serwotka said: "Our members have been treated disgracefully over the last decade and they have had enough.
"As it stands, the Government has only put aside enough money for a 1% pay rise for civil servants, despite finding extra funding for other parts of the public sector.
"When our members who work in essential parts of the economy see pay deals above 1% being offered to health and local government workers, they want to know when they will get pay justice.
"We believe a 5% pay rise is not only fair and just, but affordable - if the Government closes the £119bn tax gap and funds the public sector properly."
The PCS said its members were having to cope with increased workloads amid job cuts.
A Cabinet Office spokesman said: "We would encourage the PCS to continue to talk with officials to explore the possibilities of reform to civil service pay arrangements going forward."