Civilian defence workers in Hampshire will start a work-to-rule today which union leaders have warned could disrupt the supply of equipment to the armed forces.

The action by employees at the Defence Logistics Organisation (DLO) is in protest at the threat to jobs and the relocation of work.

The Public and Commercial Services union said thousands of workers will stick strictly to their contracts of employment, including taking a 10-minute break from their computers every hour.

The union said thousands of civilian Ministry of Defence (MoD) jobs were under threat because of plans to relocate staff in the DLO and the Defence Procurement Agency to the South West.

The proposals affect up to 4,000 staff, based at Andover, Hampshire; Caversfield, Oxfordshire; Telford, Shropshire; Wyton, Cambridgeshire and Yeovilton, Somerset, who face losing their jobs or transferring to work in Bath and Bristol, said the union.

Mark Serwotka, the union's general secretary, said: ''We had hoped that the dispute could be resolved in talks with the MoD. However, the MoD's insistence to put preconditions on the talks and their refusal to discuss options put forward by the union to resolve the dispute mean that staff will be taking the historic and unprecedented step of starting industrial action.

''This is not a step which dedicated staff supporting the armed forces across the globe take lightly and they stand ready, should an emergency situation arise, to temporarily suspend their work-to-rule to ensure the front-line gets the equipment it needs.

''They have grown increasingly dismayed over these plans which will damage the local economies of the sites affected and force families to uproot and move to one of the most expensive areas of the country without any guarantee on job security.''