New Zealand has become too Auckland-centric, said the mayor of Invercargill, TVNZ reported.

After the birth of a baby girl in Middlemore Hospital Wednesday morning, experts said Auckland has reached 1.5 million in population, and Invercargill Mayor Tim Shadbolt is not pleased.

Auckland now houses more than a third of the whole country's population.

"It's devastating for us when you have a system of population-based funding," Shadbold told TV ONE's Close Up.

"We face huge pressure... because although we represent 3 percent of New Zealand's population in Southland we represent 12 percent of New Zealand's exports and I think that is a factor that should come into play when handing out funding."

By 2030, Auckland's population is expected to hit 2 million and house 40 percent of the population.

Shadbolt said focusing on one city was not sustainable and a more balanced approach is needed to drive progress in the country.

"In Australia, for example, they said new immigrants had to spend two years outside the big cities and it did work for them," he said, adding that the policymakers should not wait until Auckland houses 80 percent of New Zealanders.

Massey University Sociologist Paul Spoonley told TVNZ Auckland was growing at a rate of between 20 and 30,000 people per year - double the rate of growth for the rest of New Zealand combined.

Deputy Auckland Mayor Penny Hulse said Auckland was not pulling people from the provinces.

"People from Auckland are moving out to the rest of New Zealand at quite a rate," she said.

Hulse also pointed out Auckland was recently voted the third most liveable city in the world, and this entices immigrants even more.

"We're growing because our families are having children and immigrants are coming to Auckland. We certainly aren't gathering up the rest of New Zealand and bringing them here."

She told the same TV program that the council was prepared to deal with the growth of Auckland, as they have a 30 year plan, part of which is the creation of more affordable housing and jobs for young people.