In a statement yesterday afternoon, the DHB confirmed the resignation.
"Dr Mackersey's expertise and dedication to the role has been acknowledged. Dr Fiona Miller is currently the acting mental health leader, mental health and addiction services, and will remain in this acting role as we complete a recruitment process."
This comes a week after the Bay of Plenty Times revealed a damning internal report into mental health and addiction services in the Bay of Plenty, which led the DHB to commit to changing the "low-trust, punitive workplace culture".
Debbie Brown, quality and safety manager for the DHB, said at the time that the mental health and addiction services teams had been under significant pressure due to the growing volume and complexity of the work, suboptimal accommodation and difficulties recruiting expert staff.
There was also a high level of risk of harm to staff working in inpatient and community teams from assault by unwell clients, and a high degree of public criticism of the mental health system, she said.
A national review into mental health services is being conducted but Brown said the DHB was also taking a "fresh focus on our current services" in the Bay of Plenty.
The DHB refused to release the full internal report, written by Rap Consulting, which was sought under the Official Information Act. Instead, it released a slideshow summary of the report shared with staff.
The summary revealed the majority of staff gave "very negative" or "negative" ratings for their workplace.
Consistent themes were "significant amount of stress and distress", the need to rebuild trust and confidence in the leadership team, and a strong desire to change the culture.
The report said a commitment was being made to improve safety, culture and wellbeing.
It was commissioned in October last year, two months after the Bay of Plenty Times published leaked emails and a letter raising concerns about staff being attacked by patients high on P or synthetic cannabis.
The Bay of Plenty Times has tried to contact Mackersey for comment.