Green Party MP Catherine Delahunty has said she will resign if her party entered a coalition deal with the National Party - a call that undermines the credibility of the Green Party's bid for more mainstream political appeal by leaving open the possibility of such a deal.

Ms Delahunty did not return calls, but Otago University politics lecturer Bryce Edwards confirmed she made the comment when responding to his questions during an interview on Friday.

"I clearly asked her: 'If there was a Green Party MP that was a minister in a National-led Government, would you resign from parliament?' She said, 'Yes I would'."

A few months ago, the Green Party amended its statement on pre-election positioning to leave open a formal agreement with National, something that had been explicitly ruled out in the past.

Advertisement

Greens co-leader Russel Norman told the Herald he was comfortable with Ms Delahunty's position.

"Individual MPs and members have strong views and that's fair enough but the decision [on pre-election positioning] as a whole is made by the party."

Dr Norman said he had heard Ms Delahunty express "similar kinds of views" before. He was unaware of other current Green MPs who felt the same way.

The Greens' statement says support for a National-led government is a "highly unlikely" prospect, and co-leader Metiria Turei said at the time that it would take an extreme shift in National's economic, environmental and social policies before it happened.

Nevertheless, it was widely seen as a bid to portray the party as a constructive rather than extremist political entity.

Dr Norman said a more likely post-election scenario for the Greens was another memorandum of understanding with National similar to the existing one under which the Greens had been able to work with them on a number of issues.

That included home insulation, pest control and cleaning up toxic sites - an area of work where Ms Delahunty has already proven her willingness to work with National.