The Hamilton City Council and the Public Service Association have clashed after half the union members who responded to an internal survey claimed they had been bullied at work.
The PSA said the result highlighted a culture of bullying, a claim council leaders dispute.
The survey was conducted in June and 54 of the PSA's 129 members completed it - which represents 5 per cent of all staff.
Of those who filled in the eight-question survey, 50.94 per cent said they had been subjected to bullying in the previous six months, and a quarter said they experienced negative behaviour weekly or more frequently.
In the report, the PSA said the results suggested "a serious bullying problem" which was consistent with feedback from members, the council's own climate survey and media reports.