Finance Minister Bill English says he wants hard evidence from Auckland Council that a shortage of land is not behind the city's spiralling house prices.
The council says there is enough land in the city for developers to immediately begin building 15,000 houses.
But Mr English says developers tell him the true number is lower and he is asking the council for more information.
"The prices in Auckland tell us that there's probably a shortage regardless of what the politicians think."
He says getting to the bottom of the true land supply in Auckland will better allow the Government to come up with an effective means of tackling unaffordable housing.
Mr English said work is under way with the council and developers to establish what sections are available on the market right now.
Auckland Mayor Len Brown told Radio New Zealand's Morning Report programme on Tuesday the figure includes sections that are ready to be built on.
He said there is enough land to build 15,000 homes in Flat Bush, Riverhead, Takanini, Hobsonville and within the broader Auckland metropolitan urban area.
Mr Brown said the land is unconstrained, zoned, has infrastructure and is ready to build on.
The mayor said Auckland's property market is hot now because people have not been buying as many homes in the last four years.
Deputy mayor Penny Hulse also stands by the council's numbers and says the Government would do better to find ways of introducing more third party funding for local infrastructure such as libraries, which currently falls to councils and developers.