Australian business groups are urging the Reserve Bank to exercise caution before considering raising interest rates, given improving signs in the economy are not yet widespread.

The New Zealand dollar is overvalued by between 5 and 15 per cent, the International Monetary Fund reckons.

Around $47,000 could be shaved off the cost of each new place built in factories under Labour's planned KiwiBuild 100,000-house scheme, an opposition spokesman says.

New Zealand's inbound migration rose to a 10-year high last month, as China overtook the UK to become the biggest source of net migrants for the first time in a decade.