Jacinda Ardern has confirmed the threshold for parties to enter Parliament would not drop before the 2020 election.
Her confirmation came after Simon Bridges accused the Government on Tuesday morning of trying to save its coalition partners at the next election by trying to lower the threshold for entering Parliament.
The National leader came out strong against the Green Party's Electoral Strengthening Democracy Bill submitted on Sunday by MP Golriz Ghahraman, which would lower the threshold from the current 5 percent to 4 percent.
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"I think that Jacinda Ardern and Andrew Little need to rule out doing this before the next election. It would be outrageous if they did," he said, adding that the three-party coalition Government is trying to "save their bacon at the next election".
"If you look at our nine years, we never proactively did anything on electoral law without cross-party support. I'm available, I'm happy to talk and discuss various constitutional issues including electoral reform, with the Prime Minister."
But Prime Minister Jacinda Ardern confirmed later on Tuesday afternoon that no changes would be made before the next election.
When asked about it in Parliament, she said: "It's clear what the position of the different parties are, but anything that we may do in this space, no, it would not happen before the 2020 election."
Lowering the threshold was recommended by an Electoral Commission review of the MMP system conducted in 2012. Justice Minister Andrew Little said the coalition Government parties have taken this into consideration.
"There seems to be an acceptance that we should change those thresholds to make them fairer. Recommendations came back from the Electoral Commission to do that," he told media on Tuesday.
He said it would be unlikely any changes would come into effect before the 2020 election: "If it's a referendum it won't be in time for the 2020 election. One view is that we should just pass the legislation and the other view is that voters should have a say."
Mr Bridges suggested the Greens wanted to lower the threshold because their polling has dropped. The latest Newshub-Reid Research Poll showed the party on 5.1 percent, down 0.6 percent, leaving them perilously close to the 5 percent threshold for a party.
When pressed on the Green Party's polling last week, co-leader James Shaw said it's normal for support parties, saying he was "actually pretty pleased that we've been able to hold our vote from the election".
Ms Ghahraman criticised National's position on Tuesday, saying the party put the country through an MMP review that "took thousands of public submissions and made a series of independent recommendations, and then nothing came of it".
She said National MP Judith Collins refused to bring the recommendations to Parliament when National was in power. Ms Ghahraman said there was "no genuine consultation".
"Simon Bridges says he is concerned about changes being passed by a simple majority in the house but the previous Government rejected the changes outright just by issuing a press release," she said.
"The best thing Simon can do is support our call for these changes to be debated in Parliament so we can see what sort of majority exists for change."
Mr Bridges said there are "processes for this stuff", adding that an Electoral Law review is going on right now by the Justice Select Committee.
For "important constitutional reform", he said it could be done through a referendum or through legislation passed in Parliament.
"But if you're going to go Parliament, you would need cross party support," he said. "We need to be signed up to that - if that wasn't the case, there would have to be a referendum."