Passport Office workers across the UK are to strike for five weeks in the spring as part of a dispute over pay and conditions.
More than 1,000 members of the Public and Commercial Services (PCS) union will participate in the action from April 3 to May 5.
Those working in Durham, Glasgow, Liverpool, London, Newport, Peterborough and Southport will walk out from April 3 to May 5 while those in Belfast will strike from April 7 to May 5.
The PCS warned the strike action is likely to have a “significant impact” on the delivery of passports as the summer approaches.
Hundreds of thousands of people have been bit by delays in passport processing in the aftermath of the Covid pandemic, with the Passport Office unable to keep up with unprecedented demand as travel restrictions eased.
A report published in December by the National Audit Office found 360,000 people waited more than 10 weeks to receive their passport in the first nine months of 2022, with similar demand expected this year.
Passport Office workers have previously joined around 100,000 civil servants in industrial action that took place on 1 February and 15 March.
The workers are asking for a 10 per cent pay rise as well as changes to their pension and protected redundancy terms.
PCS general secretary Mark Serwotka said: “This escalation of our action has come about because, in sharp contrast with other parts of the public sector, ministers have failed to hold any meaningful talks with us, despite two massive strikes and sustained, targeted action lasting six months.
“Their approach is further evidence they’re treating their own workforce worse than anyone else. They’ve had six months to resolve this dispute but for six months have refused to improve their 2% imposed pay rise, and failed to address our members’ other issues of concern.”
It comes as the Government struck a pay deal with unions representing nurses, ambulance workers and other health workers in a bid to bring an end to ongoing strike action in the NHS.
However, ministers are yet to agree new pay deals with junior doctors, who staged a major walkout this week.
The bitter dispute will rail unions also remains ongoing nine months after the first train strikes, with further strikes planned for next month.