"In 2008 the Act Party won the seat for Epsom, and 3.65 per cent of the party vote. Despite not breaking the 5 per cent threshold this party gained one MP in Epsom, plus four additional list MPs, and another party with far more votes missed out," Mr Peters told the commission.
"This is not a sour grapes argument, it's just one we have never changed our view on."
New Zealand First was a beneficiary of the one-seat rule in 1999, when Mr Peters won the Tauranga seat and brought in four extra MPs, despite the party only receiving 4.3 per cent of the vote.
Mr Peters said a new threshold of four per cent should be introduced in cases where an MP won a seat.
With regards to the party vote, Mr Peters said the threshold should remain at 5 per cent, as it kept "radical fringe parties" from getting into Parliament.
The National Party also advocated to retain the 5 per cent threshold, but rejected the idea of getting rid of the one-seat threshold, saying the status quo provided the right balance of proportionality and stability.
In contrast, Labour called for a number of changes to the system, including dropping the one-seat rule, and lowering the party vote threshold to 4 per cent.
Among the other issues raised in today's hearing, was whether the dual candidacy rule should be retained.
The rule is responsible for so-called "back-door" MPs, in that it 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 get back into Parliament on the list.
While the rule has been the cause of controversy, political parties appear to be in agreement on the issue, with National, Labour, United Future, New Zealand First, the Greens, Act and the Maori Party unanimously calling to retain the mechanism.
Another issue being canvassed in the review is the make up of party lists, and whether their should be more public input into the order candidates appear.
Once again political parties were largely in agreement to retain the status quo, with parties deciding the order. The exception was United Future, which suggested that all candidates stand for both the list and an electorate, and that the order of the list be determined by the level of party vote gained in each electorate.
The MMP review follows last year's referendum, in which New Zealanders voted to retain the current system.
The Electoral Commission is expected to deliver its final report to Justice Minister Judith Collins by October 31, after which the Government will decide whether to legislate changes.
