National Party leader Simon Bridges has hit back at Green Party co-leader James Shaw, calling him a Labour Party member at heart.
Bridges was responding to Shaw's comments at the weekend, where he told the Green Party annual conference he would never side with a party led by Bridges.
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"I would never empower someone with as little personal integrity as Simon Bridges to become Prime Minister," Shaw said.
But Bridges isn't worried.
"These guys are watermelons, we all know this, it's got nothing to do with me. They were never, ever in their wildest dreams going to go with us," he told The AM Show.
The Greens isn't even the right fit for James Shaw according to Bridges, who believes he's more of a centrist than his other party members.
"I think James Shaw is actually a Labour Party member in his heart, I think he actually ultimately wants to be part of the Labour Party.
"My understanding is all around him the other Green MPs are all with Marama [Davidson] and he's becoming increasingly disenfranchised in his party.
"But I think what the weekend in all seriousness shows is a Green Party and a leader or co-leader that's under deep pressure."
New Zealand First not an option either
National's chances of taking either of Labour's governing partners are slim according to Bridges, who called chances of a National-New Zealand first Government unlikely.
"They will pretend 'oh we can go both ways', but what we know is history, he doesn't like National. I think it is unlikely that he'll want to go with us.
"It's very unlikely that there will be a National-New Zealand First deal."
National went into Government with New Zealand First once, in 1996, but the coalition didn't last the entire term and fell apart in 1998.
The party last governed with two coalition partners, the Maori Party, which is no longer in Parliament, and ACT, which only has one MP.
Without getting enough votes to govern alone in 2020, National will need a new coalition partner or a much stronger ACT Party.