Staff at the Home Office will go on strike today in the latest phase of three months of industrial action by civil servants in a dispute over pay, jobs and terms and conditions.
The Public and Commercial Services union said there will be walkouts for the rest of the week in different sections of the department.
Staff who work in immigration and asylum, including those trying to tackle backlogs in cases, will strike today, while Border Force staff will be taking action at a later date.
The union claimed the "belligerent" actions of senior Home Office officials mean the department faces days of industrial action and disruption instead of just a half-day stoppage which hit other parts of Whitehall earlier this month.
PCS general secretary Mark Serwotka said: "These strikes come as the department faces more scrutiny for its failure to support staff and the people who rely on the services they provide.
"While other civil service departments recognise our dispute is with a Government that is refusing to negotiate with us, the Home Office appears to want to make it into a battle against its own workforce."