"This plan represents our shared vision and priorities; Labour, New Zealand First and the Greens. It establishes the foundation for the Government's work and includes issues of particular importance to each of the parties which are supported by all of them," Ardern said.
Through the 12 priority areas, New Zealanders could clearly see what the Government was doing and what its priorities were, and provided certainty on its direction and the issues it was focused on.
The plan will be reviewed every six months, to see how it is tracking, with the first review due in February 2019.
Ardern addressed the recent differences of opinion between the coalition partners, saying "perhaps it's because we have never had a government quite like ours that we cause a little bit of chat.
"It should come as no surprise though, that as three distinct parties, we will have different opinions and ideas. Those didn't begin and nor did they end at the negotiating table."
Peters put it more bluntly at the press conference afterwards.
"This is not dysfunction junction, like the previous administration. We know what we're doing," he said.
He also dismissed a suggestion he was the tail wagging the dog.
"I'm not a tail. None of us is a tail. We don't demean people with that expression. We are a seriously organised Government where we have an enormous programme, and you saw it today."
Peters said he was "extraordinarily happy" with the current coalition.
Ardern said the three parties "genuinely" worked together.
"People will already know and accept that we are three different parties. We're three different parties because actually we do have different ideas and different opinions. What the public is seeing is simply that we work through those together."
But National and ACT both wrote off Sunday's speech as a "TEDx Talk" of little substance.
National leader Simon Bridges said Ardern was "desperate to show a united Government after the shambles of the past few weeks".
"It is barely 10 months since the Speech from the Throne, which along with the coalition agreements was meant to be the riding instructions for this Government. They weren't prepared for Government and are barely any further ahead now than they were a year ago."
Act leader David Seymour called it an "underwhelming announcement".
"In a speech reminiscent of an 'all style, no new substance' TEDx talk, Prime Minister Jacinda Ardern spouted the same tax and spend policy approach we came to expect from National," Seymour said.