Judith Collins is refusing to say how many state houses National would build should it win the next election.
The number of families on the waiting list has ballooned to more than 23,000, doubling in the last two years as rents and house prices skyrocket.
When the Labour-led Government took power in 2017, there were 5844.
"It is simply unacceptable that after four years and the Government, all its promises, we've gone from about 5000 families on the state house waiting list to around 24,000. It's just a spectacular failure," Collins told The AM Show on Wednesday.
There is also an increasing number of children living in emergency accommodation - typically motels. At the end of March there were 4368, up from 3795 in June last year, despite the total number of households dropping from 4086 to 3987. A small minority have been there for over a year.
Collins, dubbing them the "motel generation", said the policy - started by National - was the right thing to do at the time, but should have been fixed by now.
"You can't go from the numbers we had to what the Government's got at the moment without looking at what it is they've done to the housing market - where you have private landlords exiting the market or people deciding not to build houses for rentals because there's no point."
In the face of record house prices, the Government has moved to reduce demand and boost supply. In March it unveiled new rules designed to make speculation and investment in existing stock less attractive, including the removal of tax breaks investors enjoyed over owner-occupiers, and making new builds more attractive by not subjecting them to the same restrictions.
As for supply, building consents for new homes are at a record high - more than 41,000 approved in the year ended March, according to Statistics NZ.
Collins says "mass consenting" is the answer, like what happened in Christchurch following the quakes. Christchurch is one of the few places in New Zealand where house prices haven't risen dramatically.
But in most regions, it's become increasingly unaffordable. Collins said it's important to build more state houses, but wouldn't say how many National would promise.
"I'm not going to tell you exactly how many, certainly not at this stage. I think it's really important that we do build state houses, but we build state houses in ways that are actually safe for people as well in terms of making sure we don't have whole streets full of gangs, as we do at the moment."
During its last nine years in power, National sold more state houses than it built - which housing spokesperson Nicola Willis has admitted was a mistake.
According to Kainga Ora data, there are 2783 more state rentals now than in September 2017 when Labour took over. Labour has promised 18,000 by 2024.
Including emergency, transitional and community housing, there are currently 4649 more places than in 2017.
But there remain fewer state rentals now (64,106) than in 2009 (65,583), at the start of National's last nine years in power. There are even fewer now than in 1993 (69,315), according to a Motu Economic and Public Policy Research paper from 2010.
The Government has repeatedly blamed the overall housing shortfall on previous Governments.
"We've said over and over again we don't want to see people in emergency accommodation, but we don't have the number of houses that we need because of the failure by previous Governments to build the houses that we need," Social Development Minister Carmel Sepuloni told The AM Show on Tuesday.
"We've got a building programme that is on track at the moment, but in the interim we still have families that are homeless that we need to provide emergency housing to."