Act leader David Seymour wants land at the foothills of Auckland's Waitakere ranges to be opened up for housing development.
Seymour this morning launched his new book, Own Your Future, at a property on Forest Hill Rd in Henderson, which lies just outside the urban boundary.
The owners, the Vitasovich family, want to subdivide the land, and their story features in Seymour's book as an example of the "red tape" he says Act will cut through.
Doing so would allow a minimum of 600,000 new homes to be built in areas like Waitakere, Karaka and Clevedon.
"By failing to open up this land for housing, successive governments are guilty of gross negligence," Seymour said.
"Land use restrictions are now responsible for 56 per cent of the average Auckland house price, according to one of the Government's own reports.
"This cost is the single largest cause of poverty, inequality and sickness in Auckland and beyond."
Seymour said if two restricted zones were reclassified as residential a further 627,525 homes could be built (223,560 hones in the countryside living zone and 403,965 in the mixed rural zone).
"These are not treasured natural landscapes. They are grassy fields with the occasional barn or horse."
The Vitasovich family land is on the edge of the Waitakere Ranges Heritage Protection Area (WRHPA). In his book, Seymour criticises locals who see development of the land as "the thin edge of the whole mountain range being developed".
"They seem to have clout in the area. Labour's outspoken housing spokesman is from the West [Phil Twyford], and he won't say boo about the WRHPA. I ask a senior National MP who lives in the Ranges, who says, 'aww well, ahh, I live up there'."