Parks, recreation and heritage chairwoman Sandra Coney said the Unitary Plan was extremely weak about identifying land for future open space.
She doubted that "worthy intentions" in the new acquisition policy would be able to create more open space within the existing urban area where most of Auckland's growth was being directed.
"So, when we attempt to buy properties for open space, we are going to have to buy at the market price with the underlying zoning being either for terrace housing or apartment buildings. We have shot ourselves in the foot by increasing the value of the land we want to buy."
Ms Coney said purchase of some important pieces of neighbouring land to expand parks had been rejected by staff because there was no money.
Chief planning officer Dr Roger Blakeley said the draft plan could not identify land it hoped to acquire for open space because "it still belongs to someone else".
The new policy said land to meet needs of communities would be identified through an endorsed spatial planning process, such as an area plan, precinct plan or structure plan.
Deputy Mayor Penny Hulse said the policy made it clear the council would seek open space to keep pace with growth.