Green Party co-leader James Shaw told Mike Hosking on Newstalk ZB this morning that despite the cannabis referendum failing by 6 per cent, he was hopeful it still could cross the line with special votes still being counted.

"We will have to wait and see the results ... I know it's unlikely but if you look at what happened on election night a lot that happened was unlikely too [sighting Swarbrick's winning of the Auckland central seat]," Shaw said.

Hosking replied: "Yeah but what you're saying to me is that just because people voted in the special votes that somehow they're dramatically different from the rest of the country which of course there is no evidence of at all."

"Well I guess we will just have to wait and see," Shaw responded.

Shaw also hit back at comment around their cooperation deal with Labour and criticism from former Green party members that they didn't have any power as they were sitting outside Cabinet.

He said he was also sitting outside Cabinet during the last term of government and got several issues signed off and expected to do the same again.

"There are some anxieties about the potential to get subsumed but ultimately our party, as you say 85 per cent of them backed the deal and I think that is because they have seen over the course of the last three years that when you are in government and have ministers that you can deliver an enormous amount.

"About 99 per cent of what we did in the last term of government was not specified in our confidence and supply agreement and we were able to do that because we had ministers, because we had that constructive relationship with our colleagues."

He said the part was "delighted" with the party's result, which saw it increase its caucus size for the first time since 2011 and win its first electorate seat - Auckland Central - in 21 years.

Asked to rate the resulting deal with Labour out of 10, Shaw gave it a 7.5 because it meant it "explicitly" preserved their ability to "constructively critique the Government".