The mayors of North Shore and Auckland City say a plan to spend $1 million on an Auckland supercity party would be an extravagant waste of money.
The organiser, the Domains Concerts Trust, says the concept has the support of Local Government Minister Rodney Hide.
The trust's Alan Smythe says the event would celebrate the creation of the supercity.
Mr Smythe says there is wide support, including from a number of Auckland's mayors, and the party would hopefully use lottery funding.
But mayors John Banks and Andrew Williams say it is not appropriate.
Mr Williams says money should not be spent to celebrate a forced amalgamation of the cities of Auckland.
Mr Hide says he is not officially endorsing the event, which he says would not be a party for the supercity, but rather a celebration of Auckland.
The Lotteries Grants Board says it has not received an application yet, and has not given event grants for such a large amount of money in the past.