British travellers making a last-minute dash to get a passport could face disappointment as passport workers began a three-day strike on Wednesday over pay and office closures.
Nearly 3,000 members of the Public and Commercial Services Union working at regional passport offices as well as 68 interview offices were expected to walk out during one of the busiest times of the year.
Interviews will be cancelled while ordinary passport applications are set to face processing delays, the union warned.
The dispute at the Identity and Passport Service (IPS) centres around a below-inflation 2.5 percent pay offer, which the union says excludes its longer-serving members who will have received no pay rise for the fifth year in a row.
Inflation is currently running at 3.8 percent - its highest level in more than a decade.
They are also striking over the prospect of four of the seven regional offices closing.
Plans have already been drawn up to close the Glasgow passport office which could see more than 100 jobs go, it said.
"The union fears that resources are being diverted from passport processing to the controversial introduction of ID cards," the union said in a statement.
The National Identity Scheme is to be rolled out for the public from 2011/12, offering everyone a choice of a separate identity card, passport or both.
Mark Serwotka, PCS general secretary, added: "The closure of the Glasgow passport office and the threat to a further unnamed three is fuelling the anger over the government's policy of below inflation pay.
"It is disgraceful that long serving passport staff should receive no pay rise for the fifth year in a row and that efficient hardworking staff should be rewarded with a pay cut in real terms."
A spokesman for the IPS said it would work to maintain a service.
"IPS regional office counters will remain open and we are able to issue passports for those in emergency situations or with urgent needs.
"Any customer who has booked for premium services or an interview will have the appointment honoured."
A cap on public sector pay has triggered a series of strikes this year.
Last Friday, coastguards, Home Office workers, immigration officers and Land Registry staff went on strike for at least a day.
Earlier, hundreds of thousands of local government workers disrupted services ranging from graduation ceremonies to rubbish collection.
The PCS, the National Union of Teachers and the University and College Union carried out industrial action last April.
The union, which has 315,000 members in more than 200 departments and agencies, said it would seek to ballot members on further strike action across the civil service if a settlement is not reached.