Labour yesterday rebuffed a proposal by the Green Party to present both parties as a coalition Government in waiting during in the run-up to the September 20 election.
Labour leader David Cunliffe indicated that such a pre-election arrangement could have posed problems with post-election negotiations with other parties, such as New Zealand First.
The Greens never had a formal coalition with the three-term Helen Clark Government, sufficing with a less extensive support agreement and no ministers.
Mr Cunliffe told the Herald tonight he envisaged that Labour would try to negotiate a formal coalition agreement with the Greens after the election, but until then he would be referring to a "Labour-led Government," not a "Labour-Greens Government" - or a "Green-Labour Government" which had also been raised.
"I'm the leader of the Labour Party and my job is to maximize the Labour Party vote," he said.
"The Labour Party will be the core of the incoming Government working co-operatively with the Green Party who are our longstanding friends.
But Labour would quite possibly be working with other parties as well "and whatever the coalition arrangements are, they need to be able to spread across more than two parties."
He said it was important to maximize the reach "all the way from the greenest end of the green spectrum right to the political centre and cross-over voters and in order to do that, it is important that they have their brand and we have our brand, and they have their policies and we have our policies."
Asked if he had a preference for a coalition agreement or a support agreement (which National uses with the Maori Party, Act and United Future) Mr Cunliffe said: "We, I imagine, would work towards a coalition agreement but after the election what we have said is that while we are happy to discuss process to ensure a smooth transition, we will not be negotiating policy towards a formal coalition until we know what the wishes of voters are."
Greens co-leader Russel Norman said tonight he was disappointed Labour had turned down the proposal.
the proposal had largely been about the language they used to describe their relationship.
"It was to present as a Government in waiting, if you like, so that voters would have a clear understanding of what the alternatives were. That was at the heart of the idea."
He said the Greens have long wanted proportionality in cabinet positions as well.
He acknowledged that National often used the term Labour-Greens Government in derogatory tones but believed it could be turned into a positive to show coherent parties that disagreed on some issues but had a way of working together.
If Labour had accepted the proposal , Dr Norman said there would also have been more joint policy launches, such as the launch on power policy last year.
"I think it fair to say that they are less likely."
Dr Norman said it was clear that Labour could not form a Government without the Greens and Labour's voted wanted it to form a coalition with the Greens.
A genuinely new forward-looking Government would need a strong Green Party there.
"The stronger the Greens are there, the more progressive will be."
Polling suggests the Labour would not be able to form a Government without the support of both the Greens and New Zealand First.
The Greens are committed to getting rid of National. New Zealand First could work with Labour or National post-election.
New Zealand First leader Winston Peters entered a confidence and supply support agreement with Labour after the 2005 election on the condition that the Greens were not part of Government.
He has not said he would definitely take the same position as 2005 if he held the balance of power this year, but when Mr Cunliffe said last month he might talk to New Zealand First first after the election, that unnerved the Greens.