You are not permitted to download, save or email this image. Visit image gallery to purchase the image.
Mr Key said he intended leading a positive, aspirational government in a second term.
"I don't see a place for a Winston Peters-led New Zealand First in a government that I lead," he said at a press conference today.
"Historically, he has always been sacked by prime ministers. It's a very different style to mine and it's rearward-looking.
"I'm about tomorrow, I'm not about yesterday."
Mr Key said before the 2008 election he wouldn't work with Mr Peters, a decision which was considered to have played a part in NZ First's failure to reach the 5% threshold of the party vote and disappear from Parliament.
Mr Peters is campaigning to get back in, with his party polling between 2% and 3% in most surveys.
Before the last election Mr Peters was involved in a scandal over party subscriptions, and Mr Key said at the time he didn't want to run a government which was like a soap opera.
Mr Key is again gambling on NZ First failing to make it into Parliament, or failing to hold the balance of power if it does.
"If Winston Peters holds the balance of power it will be a Phil Goff-led Labour government," Mr Key said.
He told reporters he decided to announce the election date at the beginning of the year because of the Rugby World Cup tournament, which ends on October 23.
"This gives the public clarity," he said.
"The Rugby World Cup is a huge opportunity for New Zealand, the biggest event it has ever staged, and we can showcase the country to billions of viewers.
"I don't want to undermine that by playing politics with the election date.
"I think the New Zealand public is sick of games, of people talking in rhymes and riddles."
Governments usually hold off announcing election dates as long as they can so their opponents are kept guessing, and Mr Key said he thought his decision to reveal it at the beginning of the year was unprecedented.
Mr Key said National could work with its current support partners, the Maori Party and ACT, after the election and had delivered stable government so far.
"National will be campaigning on our record as responsible managers of the economy," he said.
"We're taking clear steps to get the country's debt under control and to put the right incentives into the economy to drive faster, real growth."
He said the election would be about building stronger growth, building greater value for money in the public service and building a safer New Zealand.
Labour leader Phil Goff said his team of MPs and candidates would be ready for the fight.
"Labour will campaign on the issues that are affecting New Zealanders most," he said.
"We know that people are worried about the soaring cost of living with prices rising much faster than wages -- that will be a key issue this election."