He could not comment on the allegations but he stringently denied all of them.
He said with the introduction of a new chief executive to the organisation, it was an appropriate time to resign.
Corina Jordan had become the new chief executive of Fish & Game in August last year, replacing Martin Taylor.
Corina Jordan replaced Martin Taylor as chief executive of Fish & Game.
An independent review of the organisation last year found it had a bloated management structure and recommended the organisation slim the group down from 12 councils to six.
Fish & Game manages, maintains and enhances sports fish and game birds and their habitats in the best long-term interests of present and future generations of anglers and hunters.
Grubb was tasked with chairing the group that would lead the change of the organisation.
He said yesterday he had done the work to modernise Fish & Game and move the organisation to a more professional footing. But that had met opposition.
“I have been subjected to an unrelenting campaign of abuse from a small group who are opposed to the changes. They do not want change and I have been subject to this abuse for the past 18 months.”
Former Fish & Game New Zealand chief executive Martin Taylor. Photo / Mark Mitchell
Grubb became national chairman of the group in November 2020.
The abuse had led to sleepless nights and stress for him. He said none of those abusing him had had the guts to address him face-to-face and had just sent emails that were redirected to him.
He had always operated as a man of honesty in the role.
“Since I have been chairman I have conducted myself with integrity and dignity.
“That is my style and my manner.”
He said the behaviour was outrageous from the group opposing the changes.