Labour campaign manager MP Phil Twyford has called out National Party leader Bill English for "overreaching".
He told The AM Show Bill English is acting as if he'll still be Prime Minister when the deals are done, even though National failed to win a majority of votes.
"I think he's overreached a bit. He's been sounding as if he's got this commanding moral authority and mandate. He's a caretaker Prime Minister right now."
While the preliminary count shows National won 46 percent of votes to Labour's 35.8 percent, Mr Twyford says the winner of the election is the party that can form a Government - not the party with the most votes.
"In terms of the MMP process, all that doesn't matter. Now the task ahead of us is to stitch together a progressive and stable Governmentâ€¦ Let the games begin."
With the Greens not keen on backing a Labour-NZ First coalition from the outside, there are two major scenarios on the table: a Labour-led coalition with both Greens and NZ First, or a National-led coalition with NZ First.
Mr Twyford said Labour is "back in the game".
"We've worked with the Greens and NZ First in Parliament now for quite a few years. We know each other pretty well. I'm confident that there is both the policy alignment between these three parties and the personal relationships that we can stitch something together. But we all know Winston is in the box seat right now."
He said there has not yet been an official phone call.
"Winston himself said yesterday he's going to take two weeks - he's not interested in negotiating until the special [votes] are in."