Mr Peters pointed out he ran the lowest portfolio costs of any government minister in the 1990 National Government and the lowest costs of any foreign minister in recent times.
"So that's a criticism based on nothing at all. He's also made comments that I was sacked by every prime minister I worked with - that's a lie."
He also hit back at Mr Key's comments about his "stability", pointing to National's campaign promises of building new hospitals and schools after opting to pay down debt with asset sales.
"Now that's what I call unstable."
Mr Peters said he was not surprised at Mr Key's comments - but refused to elaborate on his claims the Prime Minister had been advised not to talk about him.
Speaking before 250 party faithful in the hot noon sun, Mr Peters questioned why the "teapot tapes" controversy had lead the news when "we've got a global financial crisis like you've never seen and we're up to our necks in debt".
But he repeatedly referred to the tapes, appealing to his mostly elderly audience by saying the tapes would reveal "some people think they are superior to you just because you're going grey".
He also attacked the Bay of Plenty's National MPs for missing local candidates' meetings.
"There have been candidates' meetings, but the local MPs not turning up to them," he said, referring to Tauranga incumbent Simon Bridges.
"What I expect is for them to come along and defend their record - if they've got one to defend."
He drew on his seven terms in the Tauranga seat, saying there were "more roads around here than the alphabet" when he first claimed the electorate in 1984, and in another swipe at Mr Bridges, quipped: "We all know that in my time in Tauranga, before I arrived there was no bridge and when I left, there were two ... in fact three."
His characteristically spirited half-hour speech canvassed the party's core stances, including its opposition to the sale of state assets and prime farms to foreigners and other parties' "separatist policies", singling out social services and health programme Whanau Ora and the Marine and Coastal Area Act.
With a Roy Morgan poll released on Friday showing NZ First edging toward the 5 per cent MMP threshold with 4.5 per cent of the vote, the ousted party could reclaim a presence in Parliament.
Supporter Charlie Carson thought the party's chances of returning to Parliament were "very good".
Former Tauranga Mayor Noel Pope believed the country "needs New Zealand First".
"It's just a damn shame that politics in their philosophies, rather than their practicalities, are having such a big effect on everybody."
