"Now we can get serious about attracting more members and with at least 100 expressions of interest we don't think this will be too difficult," Mr Macpherson said.
"We're off to a flying start."
Mr McVicker said the society had attracted a diverse range of Rotorua residents.
"We are not just targeting Europeans, but everyone who is interested in defending our democratic rights," he said.
The society elected district councillor Glenys Searancke as its chairwoman with academic and former Waiariki Institute of Technology chief executive Mr Macpherson as its secretary.
Rotorua accountant Len Watson is treasurer and its committee is made up of district councillors Mike McVicker and Rob Kent, along with Blanche Kingdon, Hopuruahine Wairama-Whitu and Allan MacKenzie.
Society members also include former district councillors Bob Martin, Cliff Lee, Julie Calnan and Rosemary Michie.
The society will be setting up a Facebook page as well as a website where interested people can join up.
They are especially keen to have paying members who would help cover costs for their website, advertising and promotion, and any legal challenges they may undertake.
"We need to stop the mayor and her idea to have unelected iwi members sitting around the council table, even though she denies she is driving it," Mr McVicker said.
"We will use every means we can - legal and political to support our cause," Mr Macpherson added.
They said the group would put pressure on councillors and the public to make sure the iwi proposal did not go through.
"We only need to change the minds of four other councillors, which is really all we need to vote this proposal down in council," Mr McVicker said.
"Many people see this as a very important issue and from the feedback we have received we are sure we will get a lot more support.
"Many people also feel that the mayor has rammed decisions through and don't like the fact there has been little or no consultation."
They pointed to the name change for the Convention Centre to the Sir Howard Morrison Performing Arts Centre, the council's own name change to the Rotorua Lakes Council and the Green Corridor proposal as further examples of undemocratic decisions "rammed through" council.
Rotorua Mayor Steve Chadwick declined to comment.