Border Force staff at Heathrow are due to strike for four days from today (Monday) in a dispute over changes to working conditions.
The Public and Commercial Services (PCS) union said about 300 members of staff would stop working early on Monday in Terminals 2, 3, 4 and 5.
This follows the Unite union warning that other workers will go on strike at the London hub from May 7 to May 13 over plans to outsource hundreds of roles.
The PCS union said: “The members are committed to the action and expect that their walkouts will disrupt passport checks for travellers coming into the UK at Heathrow airport.”
Union general secretary Fran Heathcote said: “It’s disappointing that despite talks last week, the Home Office is not prepared to grant any flexibility to their new roster.
“None of our dedicated and highly experienced members in the Border Force want to take strike action but the way they’ve been treated by their employer leaves them with no option.”
A Home Office spokesperson said: “We are disappointed with the union’s decision to strike but remain open to discussing a resolution with the PCS.
“The changes we are implementing will bring the working arrangements for Border Force Heathrow staff in line with the way staff work at all other major ports, provide them with more certainty on working patterns and improve the service to the travelling public.
“We have robust plans in place to minimise disruption where possible, but we urge passengers to check the latest advice from operators before they travel.”
The Home Office has not applied to use a recently passed law aimed at guaranteeing a minimum level of service during strikes, according to The Guardian.
Lisa Webb, consumer law expert at consumer group Which?, said: “Travellers will understandably be concerned about upcoming strikes and what this could mean for them.
“If you are travelling in or out of Heathrow on these days, be prepared for longer queues and delays.
“If you are in a security queue and your flight departs soon, make a fuss and let staff know the urgency. Security staff may fast-track you. Alternatively, contact your airline before the flight departs to tell them you won’t get through security in time – some, like British Airways, offer free rebooking.
“Travellers should also ensure they have comprehensive travel insurance from the date they book their trip and check the policy carefully: not all will cover them in the event of strikes by airline or airport staff, for example.”
Heathrow has previously said it has contingency plans in place for any strike action, and can avoid any impact to passenger journeys.