Fire Service Commission chair Dame Margaret Bazley has labelled the firefighter's union as archaic and difficult to work with.
Firefighters have rejected a 2.5% pay offer and say they will go on strike unless the offer is raised to 8.9% over 18 months.
From 5 August, they will attend emergencies only and will not record data, offer training, fit fire alarms, maintain equipment or do home safety checks
Dame Margaret told Morning Report the commission's offer was more than fair and appropriate in the current financial climate.
She says it is more than teachers and nurses have received, and the union has made negotiations difficult.
She says the union tries to run the Fire Service in the interests of the union and not in the interests of the community.
Dame Margaret says she has the highest regard for firefighters as individuals, but she despairs that the union will ever play a responsible role in reaching a fair wage agreement.
Warning action could be lengthy
Similar industrial action in 2009 lasted for five months.
A professor of work and employment at Auckland University of Technology, Erling Rasmussen, says that may well happen again.
He says the union is relatively powerful because almost all professional firefighters are members.
The United Fire Brigades Association says a strike of more than one or two months would affect volunteers, because they rely on professional colleagues to maintain specialist equipment and record details of call-outs.
The United Fire Brigades Association represents both volunteer and professional brigades, with more than 80% of its members falling into the volunteer category.