The number of people moving across the Tasman hit a record high in 2008, with an annual net loss to Australia of 35,400 people.
That was up from 28,000 the previous year and exceeds the previous peak recorded in the January 1989 year
Statistics New Zealand figures show almost two-thirds of the 13,100 people who arrived from Australia permanently or long-term during the year were New Zealand citizens.
Despite the outflow to Australia, the figures show a small overall gain in the number of people coming to live in New Zealand or returning home.
The seasonally adjusted migration gain was 270 in December, the first gain in four months.
On an annual basis, there was a gain in the number of migrants of 3,814. This was the lowest December year since 2000.