Auckland Council has described as simplistic a government plan to control the supply of housing land by measuring land prices.

Photo: RNZ / Claire Eastham-Farrelly

Prime Minister John Key today revealed more about the government's new tool to tackle what it considers the biggest single factor in Auckland's housing shortage - a lack of land.

Mr Key said the government would soon reveal a "national policy statement" that would override Auckland's development blueprint, the Unitary Plan.

He said the "national policy statement" would drive the supply of land, with the Resource Management Act having factors that tie into it.

"If the Unitary Plan doesn't meet the needs of Auckland, the national policy statement - because of the way it works - will drive it, mark my words."

Mr Key said the government would monitor land prices, and if they rose too much, it would trigger the release of more housing land, regardless of council plans.

But Auckland's deputy mayor Penny Hulse said if land release was the answer to rising house prices in Auckland then prices would have gone down as the council released land under the Special Housing Areas.

She said other drivers needed to be addressed at the same time, and land supply was not the big issue holding back home building.

Photo: supplied

"We've got six and half years of land planned for, infrastructure in the ground and ready to go. Government themselves have got more than 20 special housing areas that belong to Housing New Zealand that are ready to go.

"There's no shortage of places to build. Our question to government would be, perhaps you just need to get on with it."

Auckland Council will decide its Unitary Plan on 19 August. The independent, semi-judicial panel drafting the plan, which will shape Auckland's future housing, has said it will not be swayed by political comments.

Cross party support for intervention

Earlier, Finance Minister Bill English said there is Parliamentary support to step in and fix Auckland's severe housing shortage if need be.

Mr English said both National and Labour recognise that action needs to be taken to free up more land in Auckland, and Parliament can and will act if it has to.

"The signs of that are positive, if it was required. As I said it certainly is our preference that it doesn't come to that, because it is better for that community to make its own decisions."

Photo: RNZ/Elliott Childs

Labour leader Andrew Little said his party had already communicated its willingness to co-operate on issues that are an obstacle to getting development under way, but he sounded a caution.

"We have to be very careful that whatever we do at a central government level doesn't play into the hands of the land bankers and the speculators - frankly they're predators - so the solution has to take account of that."

Mr Little said consideration should also be given to establishing an urban development authority, a central government agency with a mandate to boost housing supply in Auckland.

Budget tags $100m to free Crown land

The Budget earmarked $100 million to free up Crown land for Auckland housing and another $200m for social housing places in the region.

Eventually "a couple of thousand" houses would be built on surplus Crown land bought to boost supply, Mr English said.

On social housing, instead of waiting for more houses to be built, the government would get houses from providers.

"We have more money than we can procure houses," he said.

The $200m set aside in the Budget would provide 750 social housing places as soon as the houses could be found.

Mr English said more than 500 social housing units were being built in Auckland this year, and up to 1000 a year would be built over the next few years.

"But we don't wait round for that. We have enough money now to procure 750 places but because there's a lot of competition for the houses in Auckland the government is out there competing with everyone else for the houses.

"We'll build as many as we can but it's subject to the same constraints as everyone else."

Mr English said the Budget was about the long term.