He downplayed he and Mr Peters' previous exchanges of slights and insults and believed the NZ First Leader would have gone National's way had he held the balance of power following the weekend's election.
"I don't think it's an issue of bad blood, there's been some issues over the time but in the end I'm of a bit of view myself that if we were bigger than Labour and the Greens, in the end Winston Peters was likely to follow his constitutional instincts and give us support of some form to be a Government."
He said incoming members of Mr Peters' caucus were a positive factor in building a relationship with the party.
"There's no doubt that people like Ron Mark coming in, we know them well and we've got a stronger starting relationship with them."
That said, "the ball will be in Winston's court whether he wants to have any sort of discussions at all about working on the odd thing together, but even without that, legislation requires us to build support and will try and build that support beyond the absolute majority we have".
Mr Key did not believe, given Mr Peters' determination to lead the opposition that we would want or accept some kind of formal arrangement.
"Knowing Winston and the way he operates I suspect he'll want to come out swinging when Parliament is re-established on the basis of wanting to assert himself amongst the other parties."