Public safety is being put at risk as the pressure of years of bullying mounts, say the Auckland Rescue Helicopter Trust's pilots.
The New Zealand Air Line Pilots' Association (NZALPA) are now calling for an inquiry.
It says concerns were raised about the conduct of the Trust's CEO Greg Barrow two years ago, but little action was taken, and the bullying escalated.
Mr Barrow's resignation was announced today and the Chair of its board, Murray Bolton, will be the acting CEO until someone else is recruited.
The Trust is making no comment about the alleged bullying.
NZALPA general manager Dawn Handforth said, "This is the worst case of bullying and harassment I have encountered in 18 years as a legal advocate in the aviation industry".
She said the bullying is so severe staff are taking sick leave and feel their safety and well-being, and that of the public, is being put at risk.
"It must stop now," she said.
"We need a full inquiry looking at all aspects of management and governance at the Trust, to see how this was allowed to happen and to continue for so long. This was in spite of it being raised with the Trust board two years ago and no apparent action being taken - other than more bullying and harassment directed particularly at those who complained. The board must be held accountable.
"We also want to know what action the Civil Aviation Authority (CAA) is taking and why it has not stepped in before now.
"The staff are totally dedicated to their work and are only raising this now as they feel their safety and wellbeing is at risk.
"This must be addressed before an accident occurs."
1 NEWS has approached the CAA for comment.