Ex-Greens co-leader Russel Norman says there are three good reasons why his former colleagues won't consider doing a deal with National, even if it gets them into Parliament for the first time.

"A, they campaigned not to, which obviously is pretty important; B, if they did so there would be very significant internal division, which would cause significant damage; and C, they would lose the votes of many, many people who voted for them at the last election. It's kind of a suicide note really, for the Green Party."

Dr Norman told The AM Show on Monday morning even if current leader James Shaw was keen on what's been dubbed the #TealDeal, it's highly unlikely the membership would allow it.

"The mechanism for approving a deal like this is a special general meeting - there have to be delegates brought in from across the country, there has to be a 75 percent majority in favour of any kind of coalition deal. It's a very high internal bar. It was set specifically like that so there would be a lot of consensus before you did something like that."

Under his leadership, the Greens never ruled out working with National - but openly said it was highly unlikely. Under Mr Shaw, the party signed a memorandum of understanding with Labour, and openly campaigned on changing the Government.

"I think they're pretty much bound by that," said Dr Norman.

Even if National came to the Greens with a generous package - Dr Shaw as Deputy Prime Minister, with the environment, climate change and primary industries portfolios, for example - Dr Norman said they'd be wise to exercise caution because in three years' time, they'll probably be voted out.

"We have just had an election where the Māori Party disappeared, largely as a result of getting close to National."

Prime Minister Bill English told The AM Show on Monday he'd given Winston Peters of New Zealand First a call, but he didn't answer. He is yet to call Mr Shaw, who said at the weekend he'd at least listen to what Mr English had to say.

Newshub.