The Government's support partners have been labelled self-interested for voting against a bill that would scrap the coat-tailing rule.
United Future, ACT and the Maori Party have all benefited from the rule, and were in no mood to see the back of it. The Opposition said those parties voted out of blatant self-interest and not for the good of the electoral system.
The rule means a political party that wins an electorate seat at a general election also gets to bring in more MPs - the number depending on what its party vote was.
A bill in the name of Labour's Iain Lees-Gallowaywould have ditched that provision and reduced the party vote threshold from five percent to four.
It failed by 63 votes to 58 with National, United Future, ACT and the Maori Party voting against it.
National MP Chris Bishop said the bill was all about the fact that the opposition did not like the result of the last three elections.
"They don't like them because they lost ... so they're seeking to re-litigate that through the petty political point scoring of a members bill that they know has no chance of success."
Green Party co-leader James Shaw said that public faith in the electoral system was degraded by the coat-tailing rule.
"We recognise that that's not convenient necessarily to all of the parties in this house, but there is a greater need here which is the requirement for integrity in the system and a sense of public faith that the system is a good one."
ACT party leader David Seymour said over the history of MMP the coat-tailing rule had helped both sides of politics.
He said the opposition was grumpy about it because it had disadvantaged them recently.
He said the bill was driven by self-interest on the part of the proponent.
David Seymour argued the coat-tailing rule helped make Parliament more diverse.
But Labour's Iain Lees-Galloway tore that to shreds.
"We do have a desperate shortage of straight white men in this house, and thank goodness through the one seat threshold the ethnic representation of Epsom has been able to be represented by David Seymour and Rodney Hide in the past."