Housing and Urban Development Minister Phil Twyford is so concerned about the costs of building materials he has promised an investigation.

"The Productivity Commission has estimated we pay between 20-30 per cent more for building materials in New Zealand than they do in Australia," says Twyford.

In the other camp, Building Industry Federation chief executive Bruce Kohn says the notion behind an investigation is "ridiculous nonsense".AdvertisementAdvertise with NZME.

When maverick businessman and founder of 2Degrees Mobile, Tex Edwards renovated his Waiheke home, plasterboard cost $24 a sheet.

"Anywhere else in the world, plasterboard is as cheap as chips," he says.

Edwards, who spreads his time between New Zealand and London, paid £2.75 ($5.30) for the same quality of plasterboard for his London renovation . . . continued . . .