Len Brown's Auckland Council has spent more than $5.1 million on pollsters and surveys in the past three years.
A council spokesman said about 60 per cent of the spending was required under law, mainly for annual planning and reporting.
But councillor Cameron Brewer said spending on pollsters was "out of control".
Brewer said: "Think of the improvements a local park or playground could've enjoyed with this money. Instead it's all gone into lining the pockets of private pollsters."
The figures were released to Brewer under the Local Government Official Information and Meetings Act.
"It's time to stop the spinning and get back to delivering core council services for ratepayers," he said. He suspected the polling was being done for "purely political reasons".
A further $212,237 has been spent on around 15,827 panellists that the council use to "have their say on a wide range of council issues, activities and plans".
Brown's own office splashed $162,985 on UMR Research pollsters over two years.
"This was commissioned to assist the mayor to fulfil his role leading the development of plans, policies and budgets," a spokesman said.
Brewer said the $5.1m figure was only the tip of the iceberg.