The dispute will come to a head at a meeting in Canberra on May 2. Mr Marr called the meeting in a bid to change the constitution to allow postal votes in society elections.
The letter says the meeting will be ”the most important in the Wilderness Society’s history”.
It accuses the national leadership team of a series of failures, including wasting almost $1 million on ”useless consultancies”, creating a culture of bullying and providing little campaign direction.
A central issue in the battle is an annual general meeting attended by only 14 people that the state campaigners say was called in secret so the national leadership could re-elect themselves.
Victorian campaigns manager Gavan McFadzean said that claims the May meeting was about ”democratising” the society were cynical – the intent was to protect the existing leadership. Only the national management has access to the society’s full membership list.
Mr Marr said the allegations were baseless and the management team had a responsibility to protect the society from a ”small minority group that wants to seize control of the organisation”.