Labour leader Andrew Little says he hasn't entered into any formal obligations or commitments to accommodate the Green Party at next year's election, but hasn't ruled it out.

The Green Party reportedly won't be standing a candidate in Ohariu, leaving it open for Labour to battle against incumbent, United Future leader Peter Dunne.

Green co-leader Metiria Turei has revealed she intends to run in the Maori seat of Te Tai Tonga, currently held by Labour's Rino Tirikatene.

She says she'll be campaigning for the party vote, but said there was no agreement with Labour that she would not campaign for the electorate vote in an arrangement similar to that which National have with Act leader David Seymour.

"I campaign for the party vote because the party vote is what gets me back in parliament and what gets my party back into parliament," she said.
Mr Seymour said if the two parties were to enter into such an agreement it would not be hypocritical given their previous criticism, instead it would show they were "slow learners".

"It's always been clear if you co-operate with other parties you have a better chance of success," he said.

Mr Little also put a pin in suggestions Mr Tirikatene had been told not to run against Ms Turei.

"I've absolute confidence in Rino who has been a great MP for Te Tai Tonga, he will continue to be a great MP for Te Tai Tonga and I'll be there campaigning alongside him next year," he said.

He admitted there have been some discussions between the parties as is allowed under the Memorandum of Understanding signed earlier this year, but said that was as far as things had gone.

"There are no agreements, there are no commitments, no obligations have been entered into," he said.

But Mr Little added that he believed New Zealanders were mature enough to expect campaign tactics and he was not above electoral accommodation that would enable a change in government.

It has also been suggested that Labour may leave Nelson to the Green Party but Mr Little said it would be a "huge step" for Labour not to run a candidate in a seat, and there was a process underway in Nelson.

Prime Minister John Key has also defended challenges to incumbent MPs after reports former Merrill Lynch funds manager Simon Flood will seek nomination as National's candidate in Clutha-Southland against first-term National MP Todd Barclay.

Mr Key, himself a former Merrill Lynch investment banker, entered Parliament on a challenge.

"If ultimately someone decides that they're going to challenge a sitting MP they're free to go and do that," he said.
Meanwhile the contest is heating up in Wellington Central.

Nicola Willis has resigned from her senior executive position at Fonterra to seek the National nomination, challenging list MP Paul Foster-Bell.
The seat is currently held by Labour finance spokesman Grant Robertson, but will also be contested by Green Party co-leader James Shaw.