Protesters have staged a dawn blockade of the Border and Immigration Agency's base in Portishead.
Three people chained themselves to a car near Bristol
Members of the Bristol No Borders group chained themselves to a car parked across the entrance to the centre.
They said the aim was to prevent agency staff leaving in vehicles to carry out "inhumane" dawn raids to remove families living in the UK unlawfully.
An agency spokeswoman said officers were trained to treat families as sensitively as possible.
"We only seek to remove families who are in the UK unlawfully when all appeal rights are exhausted and they have no further claim to remain in the UK," she said.
"Throughout the removal process, we take the welfare of children extremely seriously.
"Officers involved in family removals receive thorough training in procedures to minimise the distress caused to a removable family.
"All officers involved are trained to treat all members of the family as sensitively as possible."
But Jo Freeman from the No Borders group said: "Doors are kicked in and families are snatched from their beds and taken to detention centres, where they are punished for seeking refuge in this country, and taken away from their houses, jobs, schools and communities."
Similar dawn protests were staged in Portishead, Portsmouth, Newcastle and Glasgow just before Christmas.