New Zealand PM

It is only the second time the title has been given to a person of non-Pacific heritage, with former Australian Prime Minister John Howard being a previous recipient of the honour.

The magazine's editor Samisoni Pareti said each year his publication attempted to look at the person, people or organisations that had made an impact on the Pacific.

Mr Pareti said Ms Ardern was given the 2019 title because of her work at the Pacific Islands Forum to bring consensus around the issue of climate change.

Ms Ardern is pledging $300 million in climate-related assistance over four years, an increase of $100 million.

The prime minister made the announcement in New York where she is attending for the United Nations General Assembly this week along with about 140 other world leaders.

Action on climate change is high on her agenda.

In a speech to the Climate Week conference she said climate change posed a security threat to vulnerable nations including New Zealand's Pacific neighbours.

Ms Ardern said it challenged international legal frameworks.

It follows Mr Key's surprise resignation last week. Social housing minister Paula Bennett has been named as deputy prime minister.

The appointments were confirmed after a meeting of the National Party's caucus.

Mr English, currently finance minister and deputy prime minister, will be officially sworn in at Government House in Wellington later on Monday.

In a tweet, Mr English said he was "excited and humbled" to be elected.