MMP's flaws will be scrutinised in a review of the electoral system, with public feedback to be sought from February.
The Electoral Commission will lead a review of the system in two stages. The first begins in February with a call for submissions, followed by public hearings in April and May.
A proposals paper will be available in August for public comment before the commission gives its final report to the Minister of Justice, Judith Collins, in October.
As well as the proportionality of the system, the review will consider the more contentious aspects of MMP, including the thresholds parties must achieve to win a seat and dual candidacy.
The dual candidacy rule allows candidates to stand for an electorate and on a party list, meaning that in some cases, an electorate MP can be thrown out by their local constituency but can get back into Parliament on the list.