Passengers arriving in the UK next week will face travel disruption as the immigration officers' union holds its first strike in almost 30 years.
ISU, formerly the Immigration Service Union, said its 2,300 members will walk out for 48 hours from midnight next Thursday following a dispute over rosters.
Major disruption at the UK's air and seaports, as well as locations in Northern Europe such as Channel ports, Paris and Brussels, should be expected, the union said.
An ISU spokesman said: "The dispute is over the imposition of team working and changes to the roster system for members working in Border Force (passport control), which will have an adverse effect on the security of the border and on the lives of our members.
"It is not about money."
He said 83% of the union's members voted in favour of taking strike action "as they are fundamentally opposed to team working and any rostering changes which will seriously impact their work-life balance".
The strike will involve immigration inspectors, chief immigration officers, immigration officers and assistant immigration officers, he said.
An ISU spokesman added: "UK Border Agency (UKBA) management propose to radically change the way in which staff are rostered to work in a manner which will reduce the number of staff that have previously worked at passport control and completely destroy member's work life balance.
"The UKBA is a 24/7, 365 day organisation. Every person arriving in the UK, every freight lorry, every boat, plane, train, coach, car and foot passenger has to be met. There are staff rostered on duty at air and sea ports at all hours of every day and night."
The current flexible system allows staff to "balance their work and home lives" but the proposals would involve "shifts scheduled without flexibility up to six months in advance", he said.
"Staff with childcare responsibilities have been told that they must either pay for full time child care 24 hours a day, or look for another job.
"The proposed new system is too rigid and inflexible to properly control the border."
He added it would be "totally incapable of dealing with emergencies such as the recent disruption caused by volcanic ash".
He went on: "We are committed to protecting our members and voicing their views and therefore seek a halt to the introduction of team working. We remain willing to talk to the senior managers at UKBA at any stage and urge them to provide a resolution to this dispute that is acceptable to our members."
A BAA Heathrow spokesman said: "Heathrow will be running as normal so there is no need for major concern.
"Immigration staff are employed by UKBA and not by us, but we will obviously do everything we can to mitigate any disruption should a strike go ahead."
Lin Homer, UKBA chief executive, said: "We have made concerted efforts to avoid industrial action and will keep talking to the ISU.
"As always, our priority is to keep the UK border secure while ensuring the smooth travel of legitimate travellers and goods.
"We expect the vast majority of our facilities and services to remain open for business.
"It is possible that people travelling into the country may experience some delays at border control, but we will work hard to continue to keep these to a minimum and hope that passengers will welcome the commitment of those staff who are working despite the strike action to ensure we check passengers through the controls as quickly as possible."