hlöe Swarbrick says Labour is being "disingenuous" in categorically ruling out a wealth tax.

Appearing on Ryan Bridge's Magic Talk show on Tuesday, the Green MP described it as a "top priority" for her party - and said there are "ongoing discussions" about walking away from a post-election deal with Labour if they don't get what they want.

Both Labour leader Jacinda Ardern and finance spokesperson Grant Robertson have repeatedly ruled out a wealth tax, but the Greens aren't backing down.

"There are a number of different variables that have to be considered when it comes to our negotiating table," Swarbrick told Bridge.

"I very much back in the statements that have been made by the leadership on the point that actually it's really disingenuous for Labour to try and say that they're ruling anything like this out because ultimately it's the voters who will decide."

Swarbrick said there's no document listing the Greens' priorities in terms of coalition negotiations, and wouldn't give her one bottom line.

"I think that that would be massively disingenuous of me, it really depends on if we have eight Green MPs or if we have 15," she said.

"If we've got 120 we're implementing the whole Green Party policy vision document."

Bridge pointed out the only power the Greens would have would be to walk away from a coalition or refuse to support Labour on confidence and supply if they didn't get what they wanted.

Swarbrick said there are "ongoing discussions all the time" about this.

"It's all going to depend on how many Green MPs there are, how many Labour MPs are, whether New Zealand First is in the mix," Swarbrick replied.

"There are ongoing discussions all the time and I can tell you there is a variable of different opinions and it would be bad if there wasn't, that's freedom of thought.

"Ultimately it comes down to the best possible outcome and future for this country."