Christian churches are "failing to connect" with the changing face of Auckland's ethnic population, according to a study by Massey University.
The study - Changing Patterns of Auckland Religion - found that membership of all mainstream Christian denominations, except Catholicism, have fallen to a historic low in New Zealand's largest city.
In contrast, religions like Islam, Hinduism and Buddhism are on the rise.
Massey University Associate Professor, Dr Peter Lineham, who is behind the research, said the trend showed churches were "failing to connect" with people, particularly in areas with a significant ethnic diversity.
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"My study is in Auckland, where you've got a huge diversity of people who have been emerging and changing the face of the city, and what I'm showing up is they're so much changing the face of religion as well," Lineham told TV One's Breakfast.
Membership of the Anglican Church - traditionally the dominant religion in New Zealand - has fallen dramatically, with only 10% of Aucklanders identifying with the church in 2006 compared to 47% in 1926.
The religious mapping was done using information from the 2006 Census.
It showed that wealthier areas, such as Remuera and Herne Bay, had the highest concentration of Anglican believers.
"Any religion that did not engage wider than the rich, white middle-class will certainly not be growing in a city with Auckland's demographics of today," Lineham said.
The interesting thing about the study was how much the Catholic Church has grown, he said, adding that it is possible that membership of the Catholic Church could overtake that of the Anglican faith for the first time come the next Census.
"This is a very interesting pattern," he said.
"The Catholic Church have got exactly the same problem of ageing Pakeha (as the Anglican Church), and they've lost a lot of ground among Pakeha, as Pakeha become more and more non-religious, but they've gained enormously from the new populations flooding into Auckland - Fillipinos, Koreans, Indians, Samoans and other Pacific peoples.
"That means that the Auckland Catholic Church is quite representative of Auckland. It's very striking."
Lineham's study found that Hindus make up 3.5% of Auckland's population and Buddhists 2.2% - both higher than the number of Baptists and Latter-Day Saints.
Nearly one in 10 said they were followers of other religions, while Lineham said the number of people who identified with no religion at all has also increased, a trend he attributed to an increase in immigration from communist China and secular Europe.
"One of the trends that I'm picking up in Auckland, which is a bit different from the rest of New Zealand, is that I think we're past the phase of 'religion's out', and we're at the stage of 'religion's interesting, let's explore'," he said.
Lineham said in today's modern society, people were treating religion "as a commodity", shopping around until they find one which suits them.
"I call it supermarket religion actually because it seems to me that religion is now viewed as a kind of marketed thing," he said.