Statistics Minister Maurice Williamson says new Census data which show that New Zealand population growth has halved since the last Census could prompt revision of Auckland's infrastructure plans such as an increase in high-rise apartments and the construction of a city rail loop.
But Auckland Council is standing by its plans for growth, saying that Auckland is expected to grow faster than the rest of the country.
The council's planning for the next 30 years is based on the prediction that the number of residents will grow by 1 million.
Mr Williamson said the first Census data in seven years indicated that this projection was far too high.
Statistics New Zealand figures released yesterday showed that on Census night, there were 214,101 more people in New Zealand than at the previous Census in 2006. This meant the population had grown by 31,000 a year over the past seven years, compared to 58,000 a year in the previous period of 2001 to 2006.
"This is a huge surprise - bigger than Ben Hur," Mr Williamson said. "It's nearly half the growth rate that everyone had been basing their historic numbers on."
The minister said that if the slower growth rate continued, it would affect Auckland projects which were contingent on a population increase.
He cited housing initiatives and also the construction of the city rail loop, which the Government has delayed until 2020 unless Auckland's employment and rail patronage grew.
Council chief planning officer Roger Blakely said the Census details released yesterday did not reveal the extent of Auckland's long-term growth, which was historically much more rapid than other regions.
"This is just comparing one seven-year period with another five-year period. That is not the basis on which the Auckland Plan projection was determined."
The planning documents assume that the region will grow by 2.2 per cent a year. As a result, they include proposals for more high-rise, small apartments in the suburbs and 160,000 homes outside the existing urban boundaries.
The Census data showed a national average increase of 0.75 per cent in population per year, but regional growth would not be revealed until next week.
It showed that the Auckland Central electorate had exceeded its electoral quota - the recommended proportion of constituents per electorate MP - by 18 per cent. Most other Auckland electorates also showed growth which would require electoral boundaries to be redrawn.
Massey University sociologist Paul Spoonley said the previous seven years were not a reliable guide for Auckland's next 30 years because the number of people leaving the country had reached record highs during this period.
"And Auckland has more migrants, higher fertility and the ageing of the population isn't as significant as it is in other parts of the country."