Green MP Nandor Tanczos will stay in Parliament until the election after his attempts to let co-leader Russel Norman take his seat ran aground.

Mr Tanczos is retiring from Parliament at the election and had hoped to go earlier.

He wanted Dr Norman to take his seat but for that to happen, the next two people on the party's list had to step aside to let Dr Norman through.

Candidate Catherine Delahunty was prepared to, but former Green MP Mike Ward was not.

A seat in Parliament would have helped lift Dr Norman's profile going into the election campaign and also given the party access to more resources in the lead-up to the election.

There has been speculation that Mr Ward was bitter about his placing on the new party list -- initially 29 but 14 after the party membership had its say on the list's final shape -- and also over his own failed co-leadership aspirations.

But Mr Ward told NZPA he felt it was in the "best interests" of the party for Dr Norman to continue his co-leadership role outside of Parliament.

Mr Ward said he had "offered" to go back to Parliament to fill Mr Tanczos' spot.

It made "really good sense" for Dr Norman to focus on the election campaign as a co-leader outside Parliament given that Parliament was a busy place and the lead-up to the election a busy time.

"My other reason for offering to go back myself is that I'm probably the most experienced campaigner the party has. This is my 10th general election. I've done local body ones as well."

Mr Ward, who was a MP between 1999 and 2002, said there had been "robust" debate about whether he should stand aside for Dr Norman.

While Dr Norman was concerned he lacked status because he was not a MP, "I think the media take him seriously." Mr Ward said.

"I think he's getting the messages out there and I think he's doing a really good job of it."

Dr Norman appeared philosophical about Mr Ward's move, telling NZPA it was the democratic process in action.

"That was the list we submitted at the last election and obviously we need to follow that list. Mike has given it a great deal of thought and at the end of the day, that's all you can really ask of someone."

The "preferred option" had been for him to get the seat but that was not happening "so we just have to live with it," Dr Norman said.

Mr Tanczos said it would have been "good for the Green Party" for Dr Norman to take his seat.

"Of course I'm disappointed with the outcome, but I'm not critical of Mike for his position...," he said.

There had been "lively" discussion within the party, but he did not think it was a sign of division in the party, "it's simply divergent views".

But rather than let Mr Ward take his seat, Mr Tanczos will stay in Parliament until the election.

Staying on would enable him to oversee the passage into law of the Waste Minimisation Bill, which had been making slower progress than he hoped, Mr Tanczos said.