Prospective MPs may have to choose whether to stand in an electorate or go on their party's list in future elections.

They can do both now, but a review of the MMP system launched by the Electoral Commission yesterday will examine whether to restrict it to one or the other.

The review follows the referendum held in tandem with the general election last November when more than 57 per cent of voters opted to keep MMP.

Issues the review will look at include the 5 per cent threshold for parties to get into Parliament, whether list MPs should be able to stand in by-elections, and who should decide on the order of candidates on a party list.

Victoria University political scientist Nigel Roberts said people were unhappy about "back-door MPs" – electorate MPs voted out by their constituents but returned on their party lists.

In Wales, they must stand either for the electorate or on the list, but Prof Roberts said that was the "crudest" solution.

In November, Labour MP Clayton Cosgrove lost the Waimakariri seat and National's Chris Auchinvole lost West Coast-Tasman, but both returned to Parliament.

MPs who lost their electorate and returned on the list usually did not last longer than one term, Prof Roberts said.

He did not detect much public concern about newcomers standing for both electorate and list.

Prof Roberts said the ability of parties with one electorate MP to have several seats despite not getting over the 5 per cent threshold was another concern.

ACT had five MPs in the last parliamentary term despite getting only 3.6 per cent of the party vote. "People were concerned that the one-seat threshold was distorting campaigning ... that the vote of a person in Epsom was worth more than votes cast by other voters throughout the country."

Chief electoral officer Robert Peden said people could have their say by sending a letter, postcard, or "a piece of art if they think that will convey it to us adequately".

The review will not consider changing the Maori seats or the number of MPs. People can make submissions online, in person or by mail and a series of public meetings will be held.

ISSUES ON THE TABLE IN REVIEW

Whether parties should have to get 5 per cent of the nationwide vote to enter Parliament and whether those with under 5 per cent should be able to bring in multiple MPs because they win one electorate.

Whether list MPs should be able to stand in by-elections. If a list MP wins a by-election, the party is currently entitled to bring in its next list candidate.

Whether the current dual-candidacy system, meaning candidates can stand on the party list and in an electorate, remains.

The order of party lists. The position of candidates on the list affects their chances of getting into Parliament. It is currently set by the parties themselves, but could be opened up to voters.

What to do when a party wins more electorate seats than its party vote percentage would normally give it. This is called "overhang". The Maori Party was entitled to three seats after the 2008 election through the party vote, but won five electorates.

How population changes will affect the proportionality of Parliament over time and when changes in the number of electorates should be made.

- © Fairfax NZ News