Winston Peters says he 'could've been Prime Minister' decades ago

The New Zealand First Party leader says he could have taken out New Zealand's top job decades ago.

"You won't believe this but a long time ago, I could've been the Prime Minister if I was prepared to suck up to the right-wing ideology for the National Party in 1989, 1990," Winston Peters told Three's The Project on Thursday.

"I mean if you have a look at who's been the Prime Minister of this country, in some cases, it's living proof that New Zealanders can take a joke," Mr Peters said.

"There's a stack of people who have been Prime Minister who have done nothing for this country and there have been some brilliant ones."

Speaking on the Labour Party's new leader, Jacinda Ardern, Mr Peters says he expects it'll bring "a bump" to their polls, but questions how long the "honeymoon period" will last.

"I'll tell you who's going to decide this election - these people here," he said, pointing at the crowd on The Project.

"It's not what I think, what the media thinks... it's what the people of this country think, and in fact, on the 23rd of September [the people] will have all the power in the world so whatever [their] decision is, is what we all have to live with.

"I tell all my colleagues, if you're thinking about where you're gonna go after the 23rd of September, I don't think I really want you on my team. I want you going flat out, all the way until [the election] and worry about what happens on Monday after it."

Mr Peters also says claims that his "bottom line" policies will cost $10 billion a year are simply estimates by a "fellow with a very strange attitude to life who hates cats".

"Take a wild guess who that is," he joked.

"We'll seriously grow this economy, get our exports back into line and start making some real wealth, because a whole lot of people in this audience here and a lot like them are never going to buy their own house in Auckland or any major part of this country. That's sad. We need to turn that around."

The latest Newshub-Reid Research poll has put Mr Peters in a powerful position - it's likely both parties will need to work with New Zealand First, if they want to claim victory.