Civil servants at the Home Office, Border Force and two other government departments will begin a month of industrial action from mid-December.
The PCS trade union said on Friday it had built up a “substantial strike fund” and was raising more cash to cover the dispute.
Workers, including those in the Department for Transport and Defra, will take action in a bid to stop their wages from plunging in real terms.
With inflation at 11.1 per cent – a 41-year high – staff are seeking a 10 per cent pay rise as well as assurances on job security, pensions and redundancy terms.
The expected disruption to Border Force operations comes after the home secretary, Suella Braverman, launched a crackdown on people crossing the Channel in small boats.
Union chiefs said a meeting with the Cabinet Office this week has done nothing to allay their concerns.
Earlier this month, 86.2 per cent of members voted for industrial action.
PCS general secretary Mark Serwotka said civil servants were “angry” and that it was “inconceivable” that they could take another real-terms pay cut.
“They helped to keep this country running during the pandemic, and in return, have been treated appallingly by this government,” he said.
“With inflation now at 11.1 per cent it is inconceivable that they are expected to cope with yet another real terms pay cut.”
Mr Serwotka continued: “With tens of thousands of members on poverty pay it is no longer about tightening belts, but about choosing between heating and eating – and that is simply not acceptable for the government’s own workforce.
“We have made it clear to the Cabinet Office that we are available for talks throughout this period. I hope that they do the right thing and come back to the table prepared to meet our demands.
“If not, then we are prepared to do what we need to do to show them the value of our members’ work once they withdraw their labour.”
Earlier this week the Guardian reported that the army will train soldiers to replace Border Force officers who decide to walk out over the winter.
More than 500 military personnel are expected to get five days of training, beginning on Monday 21 November.
