Passport office workers began a five-week walkout, preparing Britons for summer vacation disruption.
Strikes in England, Scotland, Wales, and Northern Ireland are set to last until May 5 in a dispute over jobs, pay, and working conditions.
More than a quarter of the 4,000 Passport Office employees are expected to strike.
The Passport Office currently recommends allowing 10 weeks for a passport renewal.
“We are disappointed with the union’s decision to strike after engaging in constructive talks to find a resolution,” a Home Office spokesperson said in response to the planned strikes.
“We are working to manage the impact of strike action whilst ensuring we can continue to deliver vital services to the public, with comprehensive contingency plans in place.”
While the passport office does not intend to update its guidance as a result of the strike, hundreds of thousands of people had to wait more than 10 weeks for their passports last year.
This was due to an increase in demand as Covid travel restrictions were lifted.
Picket lines will be set up in front of offices in Glasgow, Durham, Liverpool, Southport, Peterborough, London, Belfast, and Newport, Wales.
The union said those who walk out will be supported by a strike fund.
In an effort to resolve the dispute, PCS general secretary Mark Serwotka has written to the government requesting urgent talks.
While demand has increased, the Home Office stated that “the number of passport applications remains close to forecasted volumes.”
“There are currently no plans to change our guidance, which states that it can take up to 10 weeks to get a passport,” it added.