Fire and Emergency has done an about-turn after mistakenly trying to block staff who do not show a vaccine pass from doing or providing training.
Almost 100 firefighters cannot go to emergency callouts due to the vaccination mandate.
FENZ on Tuesday extended this to trainers and trainees.
NZ Professional Firefighters' Union national secretary Wattie Watson warned FENZ that might amount to a lockout.
"They have got it wrong because they haven't done the due process," Watson said.
"You can't just start issuing instructions that affect people who turn up to work and can't undertake their normal duties."
FENZ late yesterday revoked the instruction.
"An instruction was issued regarding ... training last night in error," national manager people and workforce capability Ian Pickard said in a statement.
"The instruction has now been revoked.
"People attending ... training (including trainers) will not be required to show a vaccination pass."
The union said the mistake showed up shortcomings in decision-making by FENZ's top-heavy bureaucracy.