The Electoral Commission has been warned against lowering the party vote threshold in its review of the Mixed Member Proportional (MMP) voting system.
The commission is hearing submissions in Wellington, following a referendum vote at the general election in November last year to retain MMP.
At present, a party can gain entry into Parliament by either getting 5% of the party vote or by having an MP win an electorate seat.
The National Party told the commission on Monday that lowering the party vote threshold could de-stablise the Government.
The party's general manager, Greg Hamilton, says it supports the status quo and the 5% party vote threshold is adequate in achieving diversity in Parliament.
"We do not believe it presents too high a barrier to entry, provided the one-seat threshold remains. If stability is already the system's weakest point, let's not go down the track of further compromising stable government for very limited improvements."
Mr Hamilton says lowering the party vote threshold could also lead to more smaller parties entering Parliament and forming complex governing arrangements.
Anti-MMP lobby group Vote for Change says dropping the party threshold to lower than 4% would result in too many minor parties entering Parliament. It says at present, there are eight parties represented in Parliament and any more would fragment the system.
Labour advocates change
The Labour Party's general secretary told the Electoral Commission that major changes need to be made to improve MMP.
Chris Flatt says Labour supports lowering the 5% party vote threshold to 4% and abolishing the one- electorate seat threshold.
"For example, in the recent election, you could argue that voters in Epsom and Ohariu had a greater impact upon Parliament's and the composition of Parliament, through what has been deemed a double dip - with their electoral vote helping one party to be represented in Parliament, but their party vote also helping elect list MPs for another party."
Mr Flatt says the commission should also consider increasing the number of electorate seats, as some of the current constituencies are too large.
The Electoral Commission is expected to report back to Parliament in October this year, but it will be up to the Government to decide whether to make any changes to MMP.