Pākehā could become a minority in Auckland in just over a decade.
Statistics New Zealand forecasts Pākehā will have fallen from 65 percent of Auckland's population in 2001, to just 48 percent by 2038.
The other big shift is in the Asian population, up from 13 percent to 38 in the same period.
Professor Paul Spoonley from Massey University's College of Humanities and Social Sciences said he expected Pākehā to fall through the 50 percent threshold in the late 2020s.
He said the shift was significant and would pose challenges, such as the need to change the political make-up of the Auckland Council and its 21 local boards, where there are few Asian members.
"Are local voters prepared to see a candidate who might be a different ethnicity to themselves, as a suitable representative to themselves ? " Professor Spoonley told RNZ's Outspoken programme.
Māori in Auckland are still seeking a dedicated seat on the council, with the mayor Phil Goff seeking a law change from the government, but as a low priority.
Julie Zhu, who is 25, moved here as a child and has stood for the Green Party in both local and general elections in Botany in east Auckland.
The Botany electorate in 2014 had the highest proportion of residents born outside New Zealand at 50 percent, with Asians making up 40 percent.
Ms Zhu said a lot needed to change, as Auckland is still very monocultural.
"I think we talk about multi-culturalism a lot but in reality we are multi-ethnic, we have a lot of ethnic groups but culturally we don't embrace those," she said.
Shail Kaushal came to this country as a child from India, and at 24 is one of the youngest Asians elected in local government, sitting on the Puketapapa Local Board.
Mr Kaushal said having more local politicians from different ethnic backgrounds will make a difference.
"If you do have more diverse representation around the decision-making table, it does give those communities who are disenfranchised, who do not feel comfortable in raising those concerns - from past government experiences overseas of where they came from - the confidence that they can actually have their say," he told Outspoken.
Professor Spoonley said a different voting system might be needed in the way MMP had worked at a national level.
"I think Auckland is the test-case or the laboratory, where we get to play around - and plays probably the wrong word because it's more serious than that - and decide how we do politics and in this case, the recognition of diversity," he said.
The forecasts for Auckland's population change are based on the medium of three projected trends, but the city has generally grown more rapidly, in line with high-growth projections.