Labour leader Andrew Little has held out an olive branch to both NZ First and the Greens as he tries to build links in the run up to the general election.

Labour is to treat the Greens as "first cab off the rank" for post election talks in a signal it is firming up its plans to work in coalition with its allied party.

The two parties signed a memorandum of understanding to work together last year, but it was due to expire on election day - a sign that Labour was not certain what stance NZ First would take towards the Greens if it held the balance of power.

But in an Opposition two-step Labour leader Andrew Little on Thursday first announced he was nominating Peters for the intelligence and security committee - with the Greens support.

MURRAY WILSON/FAIRFAX NZ NZ First leader Winston Peters is to join the committee overseeing the intelligence and security agencies.

He then made it clear that in a "quid pro quo" the Greens would be the first cab off the rank and the first party to receive a call if Labour was able to build a government after the September 23 election.

"After September 23 and if the numbers go our way and I am in the privileged position of putting together a government they are the first phone call I will make. No question about it," he said.

"We haven't spent the last many-a-year now formally strengthening our relationship and working out common ground ... for it to mean nothing at all when it comes to a general election."

KEVIN STENT/STUFF Green co-leader James Shaw wants membership of the intelligence and security committee broadened - but will back Winston Peters to join it.

He said there were no guarantees, and the numbers would dictate what will happen.

"They will be the first party I will talk to to interpret what the numbers might be and what that means. It's a commitment that the relationship does mean something after the election."

But would he be prepared to leave the Greens out of government if Winston Peters insisted and Labour needed NZ First to govern?

"I think that is unlikely."

He said the fact the Greens had agreed to Peters replacing David Shearer as an Opposition representative on the intelligence and security committee "showed they have a maturity about forging relationships beyond just the Labour Party".

"There are two other Opposition parties, apart from Labour, that we work closely together with and I contemplate both being candidates for partners or support partners to form a government. But the first I will go to will be the Green Party."

Peters will join Prime Minister Bill English, Little, and two Cabinet ministers; Chris Finlayson and Amy Adams, on the statutory committee that oversees the intelligence agencies the SIS and the GCSB.

Shearer quit Parliament late last year.

The Greens were keen to have their representative replace him on the committee but they will endorse Peters, who has been a member of the committee in the past.

Peters said Labour had raised the appointment with him.

"I said I would not be interested, unless the National Party leader was to endorse it at the very start. It is meant to be non-political and across the political divide."

He was told English had endorsed it, so he had agreed. He said he had not had a chance to think about the Greens' stance.

Meanwhile, Little said the Green support for Peters was a signal of maturity, the quality of their relationship with NZ First and a signal they were ready for Government.

But Peters reiterated his long-held stance of not commenting on post-election arrangements.

"I am not going to be responding to what other political parties say they are going to do after the election. We are sticking to our knitting and the speculative academic exercises I will leave to others including a very wanton media."

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But Little's olive branch signals the Greens importance to Labour in any post-election talks.

Earlier this month, English said he was not comfortable with a Green MP being on the committee.

"They've got a deep-seated hostility to any intelligence apparatus at all, which is not a responsible attitude, and we wouldn't want to foster it," he said.

But Little, who is pushing for wider party representation on the committee, at the time said he would be very comfortable with the Greens being on it.

Little said the required consultation has taken place and the recommendation had the support of all Opposition parties.

"As a former Foreign Affairs Minister, Winston has extensive experience of New Zealand's security and intelligence agencies and so would be a valuable addition to the committee. There are currently only two places on the five member Intelligence and Security Committee for Opposition MPs. I do not believe that fairly reflects the proportionality of Parliament.

"The committee should be enlarged to accommodate other Opposition parties with significant representation in Parliament."

He said Labour were talking with the Government about this and would table an amendment when the Intelligence and Security Bill is reported back to Parliament.

Green co-leader James Shaw confirmed his party supported Peters appointment to the committee.

Asked if he would have wanted one of the slots for a Green MP, he said the party wanted membership on the committee broadened to include more parties.

He would want to see both the Greens and NZ First on it, but this was not possible under the current structure.