The Labour Party claims the planned repeal of a law protecting public assets in Auckland from being sold, paves the way for privatisation.
The measure is included in the third and final piece of super-city legislation, which is due before Parliament next week.
Labour says the bill contains an amendment which scraps the need for majority support in a public referendum, before any sale of the Port of Auckland company can go ahead.
Local Government Minister Rodney Hide says the amendment allows the new council to decide the future of its assets through a long term community plan, which requires public consultation.
He says there will also be a statuatory three year moratorum preventing the sale of shares in the assets until 2012.
Parliament is expected to debate the bill next Tuesday.
The new Auckland Council comes into being at the 2011 elections.