Most of the work in post shops is done by staff employed by Kiwibank. The bank refused to say how many employees it has in Northland, citing commercial sensitivity.
A Kiwibank spokeswoman said its staff would be the first to know of any changes before they were communicated with the public.
"We make every effort to re-deploy affected staff to other branches or roles within Kiwibank," she said.
General manager retail distribution Geoff Waller said Kiwibank has had great customer feedback from the standalone branches it had opened elsewhere around New Zealand.
"In particular, the unique spaces we've introduced are meeting our customers' needs and enabling much better in-depth financial conversations. We think the Whangārei community will enjoy this new look and feel."
But Gallagher said while services would remain, the nature and type of work for Kiwibank staff would change and that could lead to redundancies.
"The truth is people's jobs will be affected and for smaller places like Kaitaia and Kaikohe, that will be a bit challenging. New Zealand Post has been given leeway to pull the commercial levers," he said.