Former Prime Minister John Key had a staunch message to any National MPs who continue to leak against the party: "If you can't quit leaking, quit the party".

He was speaking at National's AGM in Wellington this morning, where he, leader Judith Collins and president Peter Goodfellow addressed supporters.

Collins spoke about the opportunities that lie ahead for National and how it can take power in 2023.

Goodfellow, who is up for re-election as president tonight, however, attacked the media and Prime Minister Jacinda Ardern.

But the most applause of the morning came after Key took aim at National MPs who have been leaking to the media.

"Here is my very simple advice to those who like to leak to the media – if you can't quit your leaking, here's a clue: quit the party."

The comments received rapturous applause from those in attendance.

He said even if the leakers somehow think they are doing the party good, that attitude is wrong.

"Disunity is reported as disunity because that's exactly what it is."

He said voters "hugely punish" disunity.

"The public look at it and say 'for goodness sake, if they can't run their own party, how on earth will they run a country'."

He told MPs that it was okay to disagree and to debate ideas but he said that should be done privately.

"We shouldn't do it by going behind people's backs."

Meanwhile, Key also warned National Party faithful not to underestimate Ardern.

"Some people are going to tell you that eventually the public is going to get sick of Jacinda Ardern."

But he said that was a mistake.

"It is exactly what the Labour Party said about me for nearly a decade.

"If we underestimate Jacinda and her advisers, we will be in Opposition for a very long time."