Key Points:

National Party leader John Key has defended his opposition to plans to redevelop Hobsonville Air Base, after Prime Minister Helen Clark highlighted his claim that the scheme amounted to economic vandalism.

Housing New Zealand intends to revamp the 167ha site into a major housing development of 3000 homes.

Mr Key unveiled National's proposals to improve housing affordability on Sunday, during his party's annual conference.

Yesterday, Helen Clark said she did not believe National's policies added up to housing affordability at all, and highlighted Mr Key's objections to the Hobsonville scheme, which is planned to include 30 per cent affordable housing.

"The local MP, John Key, is leading the opposition to that, and in fact described our proposals for affordable housing as economic vandalism," she said.

Mr Key defended his position last night, saying the Hobsonville plan would see Housing New Zealand undertake a development on a greenfields site on a scale and proportion that it had never embarked on before.

"In my view that site provides a wonderful opportunity for a mixed range of affordable to high-end housing, and having Housing New Zealand as the developer and as a substantial tenant would actually cause significant economic loss."

National has moved to promote its affordable housing proposals now in an attempt to pre-empt Labour's planned unveiling this year of its own housing affordability bill.

Yesterday, Helen Clark dissected National's policy, saying it added up to a programme for leaky homes, urban sprawl, the sale of state houses, and high inflation.

Labour's proposals were still in development but were likely to be partly inspired by housing initiatives in England, especially "brownfields" developments, she said.

"There is plenty of land within our city boundaries. It's a question of how intense the use is and how well planned that is.

"There are brownfields sites within our cities; in the United Kingdom they focus quite a lot on brownfields redevelopment. That is something there probably hasn't been sufficient attention given to in New Zealand."