Proposals to "out-source" work in the logistics and engineering departments of the Cheltenham-based centre were unveiled. The centre blamed falling workload for the decision.
A GCHQ spokesman said it was impossible to say how many, if any, jobs will be lost under the exercise. But, staff believe the work is likely to be transferred to a private company, with a loss of jobs. GCHQ said it will complete a study of out-sourcing options by September and any changes will be implemented as soon as possible afterwards.
"It is too early to indicate what form the out-sourcing will take and therefore to predict the consequences for the staff areas affected. However, reductions in GCHQ staff numbers will obviously result," said the statement. The centre said it could not rule out compulsory redundancies but would try to achieve any cutback through voluntary measures.
Labour's defence spokesman, John Reid, said the Government had already sought to ban GCHQ staff from being trades union members, on grounds of national security.
"They are now intending to hock jobs at GCHQ around the market to find the lowest price.", he said.