Len Brown's office has spent almost a quarter of a million dollars on polls and surveys - but won't say why, citing privacy reasons.
The Herald on Sunday asked the Auckland mayor's office for details, including the reason for each, the questions asked, the number of people surveyed and the responses.
But Brown's office withheld the information, citing the "maintenance of the effective conduct of public affairs through the free and frank expression of opinions".
Canterbury University law professor and media law specialist Ursula Cheer was surprised by the reasons given, as involvement in polls and surveys is usually anonymous.
A vocal Brown critic, councillor Cameron Brewer, believes Brown was polling himself. "I doubt the mayoral office is polling on how the call centre is performing, people's views on grass verges and what they think of choo-choo trains. I suspect it's more about whether a certain dead cat has got any bounce."
A spokesman denied the mayor had been polling his popularity levels.
"The mayor has a statutory role under the legislation that created the SuperCity to lead the development of policies that benefit Auckland and Aucklanders," said spokesman Glynn Jones.
"The research carried out over the past four years in areas such as transport assist in that endeavour."
Spending by his office since amalgamation was also well below that allowed by law.
Brown has been under sustained attacks for his infidelity, which emerged after his re-election in 2013, and for breaking his promise to keep rates low.
In a response to a Local Government Official Information and Meetings Act request for information, Brown's office also said the release of the details might "prejudice the supply of similar information".
Brewer said that was a cop-out.
"This is ratepayers' money and ratepayers deserve to know what this polling is achieving, particularly in these tight financial times."
Brewer said he was on a crusade to highlight "silly spending".
Council research manager Marcia Noda said 60-70 per cent of spending was for research required by law. The remainder were good value.
Some of the polling and surveying was community engagement for things such as developing bylaws, Noda said.