The Public Service Association says it is disappointed Wellington's mayor supports a move to outsource council staff given she has previously stood against it.
On the casting vote of mayor Celia Wade-Brown, the council voted to cut its CitiOperations staff from 35 to about 15 on Thursday.
PSA organiser Nick Kelly represents many of the council's staff and says Ms Wade-Brown's move is disappointing given her principles.
Ms Wade-Brown says services are already delivered by the council in a mixed public-private model and the decision is about having one contract that is more efficient.