Local Government New Zealand (LGNZ) has accused Auckland Mayor Wayne Brown of misinformation after the council's decision to withdraw from the group.
The decision was made yesterday, with votes from councillors tied at 10-all before Brown cast the deciding vote.
He said the membership fee is "about 640 grand" and too high, given his view of how it's spent.
"My band regularly plays at conferences when they're held in the Bay of Islands," he said yesterday.
"All getting completely pissed and dancing all night long... for no benefit whatsoever."
But LGNZ — the national association of councils — disputes his claims.
Scott Necklen, the body's deputy chief executive, said: "Firstly, our membership fee is only $350,000, I don't know where they got that from."
He added: "We've never hosted a national conference in the Bay of Islands."
Auckland's deputy mayor Desley Simpson, who also voted to leave LGNZ, told 1News the price Brown quoted included staff time.
"I just wanted to see if we could stick up for ourselves a little bit better on our own, as opposed to using an independent lobby group that represented every other council," she said.
The decision came after local boards, which didn't get a vote, had earlier submitted their views to the council.
Sixteen voted against leaving, one was in favour, another was on the fence and three abstained.
"Local boards must be absolutely gutted their plea was ignored," Necklen said, adding LGNZ estimates the move will cost thousands more than it saves.
"Auckland is set to gain... $1 million in savings from one of our street light programmes, so they now miss out on that," he said.
"They get access to networks across the country, opportunities for Māori and Pasifika... [and] young elected leaders [are] going to miss out on opportunities."
Brown wasn't available for comment today, but Simpson disputed Necklen's assessment.
"I believe we can do it better ourselves."