Nearly 90 complaints, which include bullying and sexual harassment, have been upheld against Fire and Emergency New Zealand staff since 2016.
That's led to 15 volunteer personnel being either dismissed or discharged.
One of the complaints was against well-known senior fire investigator Mike McEnaney, who was stood down over a bullying complaint from a female firefighter in 2015.
She told the Herald last October that the toll of the near-two-year-long investigation into her complaint drove her to try to take her own life three times. McEnaney's employment was brought to an end in July 2016.
The new figures released under the Official Information Act show that of 134 misconduct complaints FENZ received between January 2016 and May 2018, 89 were upheld.
Of those upheld, 13 complaints related to bullying, five led to criminal charges, six related to harassment or sexual harassment and 46 related to inappropriate behaviour.
Several investigations are still ongoing.
FENZ's CEO Rhys Jones told the Herald the "vast majority of our people do a fantastic job and are well respected by the public and by their own people".
"But in an organisation of 14,000, there are bound to be some people who don't toe the line."
In July 2017, the Fire Service changed its name to Fire and Emergency New Zealand and vowed to change its culture.
Jones said they had made "great progress" over the past year.
"It's been a personal crusade of mine to ensure that we are creating a culture an organisation that we want it to be and to move away from any bad behaviour that we've had in the past."
When asked about some one to two year-long investigations into complaints the Herald is aware of, Jones agreed it wasn't good enough. He said some issues were quite complex and took time to resolve.
There was a long pause from Jones on the other end of the phone when asked what the criminal charges were related to in the five cases.
Also, when asked to discuss serious complaints involving at least two senior employees the Herald is aware of, Jones said:
"We consider that appropriate action is taken at every level."
He said he stood by their handling of complaints.
"We have very good mechanisms to support anyone who comes forward with a complaint. The issue is coming forward," he said.
"But once they do put their hand up and say there is an issue we do provide a lot of personal and direct support but how it's dealt with will be totally depend on what the actual issue is."
He does however admit there's work to be done and some people were "still to be removed or get corrective action".
FENZ has recently commissioned an independent review of its workplace policies to address bullying and harassment.
"We've asked Judge Coral Shaw to head up a review into what else can we do. We think we've got good systems but any improvement, any new ideas are very welcome."