Hundreds of Border Force officers working at passport control at Heathrow Airport will launch a three-day strike on Friday in a dispute over rosters.
The Public and Commercial Services union (PCS) said more than 500 of its members at terminals 2, 3, 4 and 5 are taking action in protest at new rosters being imposed.
The strike on May 31, June 1 and 2 will be followed by three weeks of action short of a strike, that will include an overtime ban from June 4 to 25.
The union said more than 250 staff face losing their jobs or being moved on to other work against their will.
Those who remain will have longer shifts, inflexible shift-swapping rules, no clarity on booking leave and no way to work around caring responsibilities, the PCS claimed.
A petition has been launched in support of the workers.
PCS general secretary Fran Heathcote said: “We call on all trade unionists and the public to support this petition and tell Border Force management to scrap this unwelcome and unworkable roster that has already caused misery to our members.
“PCS has repeatedly called for more flexibility in the new roster but management has refused to listen.
“Until they do, and they put forward proposals to improve the roster, then the dispute will continue.”