New Zealand is the second-most desired country for potential immigrants and letting everyone in would see the population almost treble, according to a survey.

The country rose to second spot as the most popular migration destination, behind Singapore, in the Gallup Potential Net Migration Index.

New Zealand was third when the list was first compiled last year, with a net migration index value of 175 per cent. Respondents were asked: "If you had the opportunity, would you like to move permanently to another country, or would you prefer to continue living in this country?"

Researcher Elsie Ho, from the University of Auckland's School of Population Health, says New Zealand's clean, green image and the perception that it is a safe country was a drawcard.

But she said it was "impossible to envisage" the country's population hitting over 12 million in the near future.

"Before we can even think of the economic benefits that brings, we have to consider the possible conflict and tensions if such numbers are let in," Dr Ho said. "New Zealanders may be more accepting of immigrants who come from similar backgrounds, such as Britain and America, but not so with migrants from Asia, Africa and the Middle East for example."

In terms of absolute numbers, the United States remained the preferred destination of most would-be migrants, but the impact is less acute because of the already large 300 million population, a spokesman for Gallup said.

The US is number 14 on the net migration list, and its population would rise by about 60 per cent if all who wanted to enter the country and those who wished to leave did.

Most poorer countries, especially in Africa and Latin America, showed net outflows, according to the poll.

Bottom on the list is Sierra Leone, whose population could plunge by 56 per cent if everyone who wanted to leave could and everyone who wanted to move there did.

"While Gallup's findings reflect people's wishes rather than their intentions, the implications of what could happen if these desires become reality are serious considerations for leaders as they plan for the future," the researchers said.

New Zealand's estimated population stands at 4.37 million, up 51,900, according to figures released this month by Statistics New Zealand.

The growth was due to 35,400 more births than deaths, and net migration gain of 16,500. Second and top positions were taken by Saudi Arabia and Singapore in last year's index.

The index is calculated on the number of adults wishing to leave a country permanently subtracted from the number who wish to immigrate to the country as a proportion of the total population. Nearly 350,000 adults in 148 countries were interviewed.

Top six countries with highest potential net adult population gain
1. Singapore +219 per cent
2. New Zealand +184 per cent
3. Saudi Arabia +176 per cent
4. Canada +160 per cent
5. Switzerland +150 per cent
6. Australia +148 per cent
(Source: Gallup)
Asians face discrimination more than any other racial groups, a study has found.

The discussion paper Confident, equal and proud? - on the barriers Asians face to equality in New Zealand - will be presented today at the annual Human Rights Commission diversity forum in Christchurch.

Co-author James Liu said Asians were the most discriminated against and earned the least income, despite barely featuring in social welfare statistics.

Migrants felt most discriminated against in public places, employment and while shopping, according to a Department of Labour immigration survey.

In Christchurch, nearly all 36 Korean migrants interviewed said they had experienced harassment in the city.

In Nelson, 81 per cent of 184 migrants surveyed also said they had experienced racism personally and 86 per cent had witnessed racist incidents.

The commission is developing a national strategy towards combating racism and discrimination against Asians.