Having recently been elected onto Hastings District Council, along with fellow councillors of Maori descent, Henare O'Keefe, Jacoby Poulain, and Adrienne Pierce, I can attest to the fact that the best way to get Maori representation in local government is for Maori to get out and vote (see my opinion piece 23 Sep 2016).
Holding a referendum on Maori Wards is a waste of time and money because the numbers simply don't stack up.
The Hastings population is around 25% Maori and historically the majority do not vote. But even if all eligible Maori did vote, Maori wards would still likely lose because the majority of the non-Maori population would vote against it.
An easy way to test this would be to undertake a simple poll before going through with a full referendum.
The big question however is what would the human cost be? Holding a vote on Maori representation would divide the community on racial grounds.