Net migration in New Zealand is the highest it has been since at least 1978 -- and possibly ever.

More than 124,000 people arrived in New Zealand in the March 2016 year, intending to stay long-term or permanently. A During the same period, 56,450 emigrated -- resulting in a net gain of 67,619 people -- the highest 12 month figure for any period in at least 38 years.

Net migration is the number of people who arrived to stay for more than 12 months, minus those who emigrated. One quarter of arrivals were accounted for by New Zealand citizens returning after being away for more than a year.

Multicultural New Zealand executive director Tayo Agunlejika said immigration was overwhelmingly beneficial to New Zealand, and helped create a diverse and dynamic culture.

"It's a very positive thing -- it gives you a vibrant society where not everyone is the same. It comes with its own challenges, but it's good for society," he said.

He said the most difficult factors for new immigrants were culture shock and isolation.

"They have to start fresh with social capital, and for some of them there's a language barrier, too. Some of them don't get employed in an area related to their skills and experience, but for most people it's the cultural shock," Mr Agunlejika said.

Compared to the March 2014 year, more immigrants arrived from 30 of the 33 nations listed this year.

Australia accounted for more than 25,000 arrivals, with many likely to be returning Kiwis. More than 45,000 people arrived from Asia, and 27,000 from Europe.

Mr Agunlejika, who is originally from Nigeria and has lived in Upper Hutt for the last 12 years, said many immigrants were still poorly treated because of their ethnicity -- an area he was trying to improve.

"We still have the challenge of discrimination. We're trying to run a campaign to encourage people to realise it's okay to be different - that being different is positive and it makes a rich society. You don't need to be afraid if people are different to you. It's difficult to overcome but it's about educating people," he said.

In the March year, 1862 more people moved from Australia to New Zealand than the other direction -- a stark contrast from 2012, when almost 40,000 people a year were leaving across the ditch -- more than 100 a day. Between May 1991 and September 2014 -- a period of 281 months -- 280 months had a net loss of migrants across the Tasman.

All regions had a net gain of international migrants in the year, but more than half of all arrivals said they would live in Auckland.

Permanent and long-term arrivals to NZ -- year ended March 2016

Australia 25,767

India 13,486

United Kingdom 13,445

China 11,722

Philippines 5476

USA 4326

Germany 4033

Arrivals by visa type -- year ended March 2016

Work 38,620

New Zealand and Australian citizens 36,355

Student 27,704

Residence 14,735