NZ First leader Winston Peters says he hasn't discussed coalitions ahead of an election in 23 years.

NZ First leader Winston Peters doubts it was "deliberate" but says Labour leader Andrew Little is wrong to say there are plans for the two parties to jointly campaign on policy.

Earlier on Sunday Little said he was talking with both the Greens and NZ First, separately, about issues where there is common ground that they could campaign on ahead of next year's general election.

He said the public would know "well in time for next year's election" where all three parties line-up and where there are differences.

DAVID WHITE/FAIRFAX NZ Labour leader Andrew Little is firming up what a coalition government would look like with the Greens.

"In terms of specific joint policy announcements, we're certainly not there yet, but between now and the next election I certainly wouldn't rule out (joint policy) with either of those parties."

But Peters says his position not to discuss potential coalition governments, or joint policy, hasn't changed in 23 years and he "won't depart from that now".

"We row our own boat and we formulate our own policy."

Peters didn't think Little had been "deliberately wrong" in his comments because the two parties do meet to discuss issues, but not policy ideas.

"It's a fact to say we've had talks on various issues...I have conversations with most political parties, but not all."

But he said those meetings centred on specific issues, such as, the conduct of the House and Question Time.

As for a joint policy announcement between Labour and the Greens - the first of those would be made in the next couple of months, according to Green Party co-leader James Shaw.

He wouldn't confirm what the subject of the proposed joint policy was as he didn't want to "let the cat out of the bag prematurely".

Little said he had discussed environmental, social and economic ideas with both the Greens and NZ First, separately.

The first taste of the idea came on Sunday with the Green Party announcing its plans to strengthen Kiwibank by injecting $100 million of capital.

While its a step removed from joint policy, Little said Labour supported the idea and would look at implementing it in a coalition government.

"There's certainly nothing we're allergic to in this proposal," he said.

The idea is to repurpose Kiwibank so it can compete against the big four foreign-owned banks, which the Greens say will lead to better interest rates.

To do this Shaw said his party would inject a further $100 million of capital into Kiwibank to "speed up its expansion into commercial banking".

The policy also includes allowing Kiwibank to keep more of its profits to help its growth and giving it a "clear purpose to lead the market in passing on interest rate cuts", Shaw said.

While Little supports the idea he says, "$100m is only a drop in the ocean for foreign banks," so it wouldn't single-handedly solve the problem of banks passing on the best interest rates to Kiwis.

He stands by his position to strong-arm banks and legislate if necessary.

"It's not an alternative. I don't think the capitalisation of Kiwibank to the extent the Greens are talking about is going to necessarily change the conduct of the overseas trading banks, if anything it will invite them to retaliate," Little said.

While "beefing up Kiwibank" was the Greens first preference, Shaw said they would be open to looking at other options if it didn't work.

Sign up to receive our new evening newsletter Two Minutes of Stuff - the news, but different.