Well it's muddy.
Firstly there's the fanciful theories of Greek/Egyptian/other settlers but these never get presented with any credible evidence SFAIK eg http://www.nzherald.co.nz/northern-a...ectid=11086095, and http://news.tangatawhenua.com/archives/18030. So let's kick all that into touch and forget about it.
Secondly, and more credibly, is the debate as to the Moriori. Polynesian/Melansian peoples who definitely lived on the Chatham Islands (and part of NZ wider dominion). Pacifistic, non-violent, and deliberately invaded, killed and enslaved, banned from intra-marrying, and forcibly assimilated by the Maoris in the 1830s. http://en.wikipedia.org/wiki/Moriori_people
Debates as to whether they were on NZ mainland before the Maoris have raged for at least the last 100 years. People side for and against and there's never been a hard definitive answer SFAIK, but the state museums I went to in NZ stated they were there first. Now Wiki says this is discredited in the 1960s, but again, the state museums in NZ I went to this (21st) century were stating they were the first settlers of NZ, as were several books I read on NZ during my travels. It all gets rather political as the Maoris depend on them not being there to get a lot of the privileges and claims they lodge to the NZ government. If a government study supports Moriori it is jumped on as anti-Maori, so one of those classic cases where a truly independent study of great detail is required. But getting both sides to commit to accepting its findings will be a something of a problem.
Whether or not the Moriori were on the main islands first, it is clear that the Maori did to them far worse than the British did to the Maori. Therefore it is hard to have much sympathy for the Maori's and their beef with the British (now NZ white) settlers. They're now going so far as to claim the seashore and seabed belong to them. All of it. WTF? http://www.teara.govt.nz/en/video/34...ore-and-seabed
http://www.legislation.govt.nz/act/p...DLM319839.html
http://www.teara.govt.nz/en/law-of-t...ore-and-seabed