Thousands of passport workers are staging a 24-hour strike on Friday in a dispute over pay.
Passport applications are set to be disrupted by the strike
The Public and Commercial Services Union said 2,500 of its members would be walking out.
The strike will affect offices in London, Peterborough, Durham, Belfast, Liverpool, Glasgow and Newport.
The action is in protest at the lack of a pay offer two months after the settlement date and will be followed by a week-long work to rule.
The union has warned that processing of passports will be "severely disrupted" by the action.
Workers have also voiced anger that the cost of a passport had risen by 50% in the past year.
General secretary Mark Serwotka said: "The union has been pressing for a formal pay offer, but management have shown a distinct lack of urgency by dragging their feet and cancelling pay negotiations.
"Members are angry at the apparent inertia of the employer who had stated that it wanted to settle this year's pay as quickly as possible.
"Staff fear a repeat of last year when it took management over a year to make a formal pay offer.
"Those taking strike action on Friday will be demonstrating that they are not prepared for the agency to carry on dragging its feet."