"There's not a dog show of that," Mr Key said.
However, Mr Key would not rule having Mr Peters as speaker, saying "anything is possible".
The lively debate saw potential coalition combinations discussed on the back of a 3News poll this evening that saw National's support slipping in the final days of the campaign.
Mr Cunliffe said that poll meant "Labour plus the Greens plus NZ First has more than National plus its ragtag of right wing weirdos".
Mr Key insisted Labour would still need the Internet Mana Party to form a Government.
"Not on the poll tonight," Mr Cunliffe said.
"I'm with you - I don't want Dotcom's mates, you're more than welcome to them," Mr Key said.
Mr Key said National was confident of getting the 47 per cent National received in 2011 and while he said he was unsure how his potential coalition partners would fare, "we will have options".
He turned to a meat metaphor to tell viewers how to vote.
"It's as simple as this - if you want to have steak for dinner tonight, go into the supermarket or the butcher and buy steak tonight, don't buy a lamb chop. If you want National to lead the Government, give your party vote to National."
On the spying issue, Mr Key said he had offered more transparency on the activities of New Zealand's security and intelligence agencies than any other prime minister, but it was important not to reveal details of New Zealand's defences.
The reason New Zealand had such agencies was the country faced "real threats, and as prime minister of New Zealand I can either choose to walk away from New Zealanders or choose to do my job. I will never walk away".
But on the Speargun project revealed by visiting US journalist Glenn Greenwald, Mr Cunliffe said it should have been called "Trojan horse" as Mr Key had not been upfront about it in the first place or the GCSB legislation Greenwald linked to it.
"New Zealanders have a right to be protected but New Zealanders have a right for their privacy to be protected unless there's a good reason for that to be overrided," he said.
Greenwald's sponsor Kim Dotcom got a mention from Mr Key when Hosking asked if he had any regrets about the campaign.
"We haven't had a chance to really have those discussion with New Zealanders on those real issues - too much time has been spent on one individual and not enough time on what is really important."
Mr Cunliffe also complained that "static" had kept the real issues from being debated.
Clashing on the economy, Mr Cunliffe again said while Mr Key and National had competently steered the country through the global financial crisis and Canterbury earthquakes, they lacked the vision and policies to steer the country into "high value segments".
Mr Key said he stood by his record of overseeing "extremely strong growth" over the last six years and said of Labour's policies that they could put in place new taxes, costs and regulations, "but there isn't a business person that will tell you that will drive growth".
Asked about their future beyond Saturday night, Mr Cunliffe said he had not given any thought to what he would do if Labour lost.
Mr Key said he didn't have a Plan B.
He had no plans of stepping down later in the term if he won and wouldn't rule out trying for another term in 2017.
"I'm 53 I'm pretty young."
