Former National Party finance minister Ruth Richardson says MMP has resulted in weak government and New Zealand should return to First Past the Post.
First Past the Post (FPP) was the electoral system used in New Zealand up until 1996 and is still used in Britain. It is one of the alternative systems on offer in the referendum on the electoral system to be held on 26 November, along with Preferential Voting. Radio New Zealand political reporter Julian Robins profiles these options.
When New Zealand voted to adopt MMP in 1993, the country abandoned more than 100 years of experience using First Past the Post.
The system tends to deliver strong, single-party government - and Ruth Richardson says that is something worth having.
"If you're looking for a regime that will throw up governments that can exercise swift and resolute initiative in the face of the circumstances that they have to deal with, and I think that is the real strength of First Past the Post - a government can govern."
First Past the Post is the most straightforward of the electoral systems on offer in this year's referendum. You get one vote to pick your local Member of Parliament and the candidate who gets the most votes wins.
Ms Richardson says the system delivers real mandate to individual MPs.
"The big parties tend to be big tents - they're broad churches, so you will get contestability of views inside of the caucus.
"You will tend to see then a process that is productive of higher quality policy and, more importantly, there is the ability to carry through gold standard policy, rather than see it diluted or eroded in the face of the endless negotiation."
First Past the Post tends to favour the major parties and is not proportional.
In the 1981 election, Social Credit gained almost 21% of the vote but won just two electorates. And in the 1978 and 1981 elections, National won more seats than Labour and formed the Government, despite winning fewer votes overall.
Sandra Grey, from the Campaign for MMP, believes First Past the Post is simply unfair.
"People were very, very unhappy with both Labour and National getting into Parliament, getting into Government and ramming through very unpopular changes for the society, very unpopular changes for our economy - and doing it against the will of the people."
Preferential Voting is used in Australia and is similar to First Past the Post.
But instead of just ticking one name, voters rank the candidates in order of preference. To win, a candidate must get more than half of the votes cast.
If no-one gets a majority of first preference votes, the lowest polling candidate drops out of the running and their votes are distributed to other candidates based on voter rankings. That process is repeated until one candidate secures more than half the votes.
Therese Arseneau, from Canterbury University, says like First Past the Post, Preferential Voting usual delivers one party a majority in Parliament.
"It's considered a system easy to throw the rascals out - both in terms of simple lines of accountability, in terms of knowing who your local electorate MP is and also you tend to have single party majority governments, so again you know who is responsible. It is a system where you can actually defeat governments."
But Dr Arseneau says there is no guarantee of single party government under either system, with the governing parties in Britain and Australia currently relying on votes from other parties and independents to secure a majority.