"National's behaviour since the election has only confirmed the good sense we had in choosing to go with Labour," he said to applause and murmurs of "hear, hear".
"National is leaderless, it's moribund, it's vacuous, it's got bitter and jealous. And it's a shell of its former self because it's been seduced by big money and marketing. Substance will always trump shallowness.
"Remember this. Simon Bridges will not lead National into the next election. He's a desperate man."
Peters said NZ First's strategy was underpinned by two things – being a constructive coalition partner, and going into the election with solid achievements.
He said the party's opponents and an "uncritical and mindless" media swarm had conspired over the past month to paint it as the opposite.
"Let us assure you nothing could be further from the truth. We gave our word about being a constructive force in the coalition. We have kept our word and the Labour Party appreciates it."
Peters' half-hour speech ran on that theme throughout, saying the party had its best ever caucus, it was polling well, it was making solid progress on delivering its promises and the gains it achieved in coalition talks.
Any reports suggesting otherwise were the mischief of the Opposition and the media.
Peters said almost 1100 items had gone through Cabinet, but the media was focused on four policy areas that were still works in progress.
"More fool them because nearly all of those four works in progress are settled. In fact they were being settled as the divisive headlines were going out."
Asked by reporters afterwards how NZ First might negotiate next time round, Peters said National could reform itself and find a leader. "It ain't got one now."
"New Zealand First has never changed. Unlike all the rest, we don't do deals behind the voters' back, so we're not going to change after 25 years."
Peters said there were plenty of people in the National caucus who believe he was right when he said Bridges was not going to lead the party into the 2020 election.
"No party can stand that sort of lack of leadership and survive long."
His speech was just what the crowd wanted to hear, the success of a resurgent party against the odds and with a bright future.
But Peters did not announce any new policy or even introduce a new turn of phrase in a delivery that was a summing up of the party's highs and lows since it was founded in 1993.