Staff at the Liverpool-based Criminal Records Bureau will start a work to rule which union officials warned could double the time it takes for prospective teachers, nurses and foster parents to obtain clearance to work with children.

Up to 450 members of the Public and Commercial Services Union at the organisation will take the action in protest at a 0.5% pay rise.

The union will urge its members to refuse to work overtime and not to exceed targets for processing criminal record checks.

These take around four weeks but the union said it could now take more than eight weeks because of the action.

The action comes during the final week of voting by all 270,000 members of the union for strikes over the government’s public sector pay policy.

If civil servants vote in favour there could be a fresh wave of industrial action later this year following a series of strikes which have already hit job centres, passports, coastguards and other government departments and agencies.

A CRB spokesperson said: “The CRB does not expect that the planned industrial action by PCS union members at the CRB from Monday 13 October will have any significant impact on its ability to delivery its service to its customers. The CRB will remain open for business as usual.”