Wellington: New Zealanders are migrating to Australia in record numbers following the Christchurch earthquakes, official data showed on Tuesday.

The net number of people leaving New Zealand for Australia in May this year was 3,300, Statistics New Zealand said, eclipsing the previous monthly high of 2,900 set in 1979.

Government statistician Geoff Bascand said a high proportion of the exodus came from Christchurch, with some 800 departing permanently in May, compared to 500 in the same month last year.

He said the number of departures increased after a devastating 6.3-magnitude earthquake hit New Zealand's second largest city in February, killing 181 people.

The quake followed a 7.0-magnitude tremor in September.

"Since the earthquake on 22 February, the city has experienced 1,300 more departures and 400 fewer arrivals than in the same period of 2010," Bascand said.

New Zealand and Australian citizens enjoy reciprocal residency arrangements, meaning New Zealanders can move to Australia and find work without applying for visas.

Another factor attracting Kiwis across the Tasman Sea is the relative strength of Australia's resource-driven economy compared to its New Zealand counterpart, which has experienced muted growth in the past 12 months.

A study by the New Zealand Institute of Economic Research last year found the average Australian family had USD 14,600 more disposable income a year than its New Zealand equivalent.

The last mass migration of kiwis to Australia was in the late 1970s and early 1980s, when the economy was reeling from global oil price shocks and high unemployment.