The biggest political party has one MP
It's unofficial. The Maori Party is the biggest political party in the country, with nearly 17,000 members, all thanks to the Governments handling of the Foreshore and Seabed legislation. This is likely to be larger than the combined membership of ACT, NZ First, United Future, Greens and the Progressives. I am flicking through Raymond Miller's book, Party Politics in New Zealand, which states that there are about 50,000 people belonging to political parties in this country. Either people have switched to the Maori Party from other parties or the Maori Party has got some new recruits. I suspect many of the Maori Party members are former Labour members.
As at the last election, one percent of voters had active party membership, with the biggest age bracket listed as those over 60. Most people have some interest in politics - usually limited to elections.
Ironically, it appears that the biggest political party will have just a handful of MP's in parliament after the election, but, in terms of seats in the house, should be the fourth biggest party in Parliament if the Green's support dips. Also, the party with one MP probably has many followers who do not realise that the party vote is the most important under MMP.