The New Zealand dollar dropped to a six-week low today after Reserve Bank governor Graeme Wheeler called the kiwi's strength "unjustified."

The Kiwi dollar shed almost one cent against the US after Reserve Bank governor Graeme Wheeler said the currency's strength was "unjustified"

The Reserve Bank governor Graeme Wheeler has raised the official cash rate as expected - leading the kiwi dollar to instantly take a tumble.

Finance Minister Bill English said the Kiwi dollar, which hit a record on a trade-weighted basis this year, is "unsustainably high".

The Kiwi dollar extended its slide as the crash of a Malaysian jet in rebel-held Ukraine and a ground offensive in Gaza sapped risk appetite worldwide.

House sales fell in June from a year earlier, led by properties of $400k or less, indicating the LVR restrictions are curbing demand at the cheaper end of the market.

New Zealand's dollar is the most overstretched in three years, trading patterns suggest, putting in jeopardy its chances of surpassing a record high.

The New Zealand dollar touched a 13-month high against the euro overnight.

The Reserve Bank has revised up its estimate of the economy's potential or non-inflationary growth rate next year, but it is still shy of the levels prevailing between the mid-90s and mid-2000s.