Border Force staff at Heathrow Airport have voted to strike in a dispute over shift patterns.
The Public and Commercial Services Union (PCS) said 600 of its members, who carry out immigration controls and passport checks, voted 90 per cent in favour of strike action.
No dates have been announced for any industrial action, but walkouts could begin as soon as April 8, said the union.
The PCS said its members are angry at planned alterations to their shift patterns that would have a detrimental effect on them and leave nearly 250 without a job on passport control.
If they refuse to accept the new contracts, they would be forced to seek jobs elsewhere in the Home Office, said the PCS.
PCS general secretary Fran Heathcote said: "Our hard-working members in the Border Force are being forced out by a belligerent employer.
"It's clear from today's ballot result how angry and determined our members are to protect their jobs.
"It's not too late for the Home Office to do the decent thing and drop these unnecessary changes and work with the union to protect jobs and working conditions.
"PCS is currently challenging the Government's minimum service levels legislation in the courts.
"We will vigorously defend our members' right to strike if ministers try to impose a work notice."
