John Key

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.

Called it "the hardest decision I've ever made," an emotional Mr Key said "I don't know what I'll do next".

Deputy PM Bill English is likely to take over until the National Party holds a caucus to choose a new PM.

Mr Key, a popular leader, is stepping down at the request of his wife Bronagh, the New Zealand Herald reports.

He won a third term for the National Party at elections in September 2014. He said he would not be contesting the 2017 election.

'Nothing left'

During the launching of the Jonah Lomu Cup in Port Moresby, Fautua said he will make strong representation for PNG to be included in the NZ$10 million (K20 million) Pacific Sports Partnership Program (PSP).

The PSP is focused on the development of rugby and netball in the Cook Islands, Fiji, Tonga and Samoa.

However, Fautua says PNG has to prove to itself and to the region that it is worthy of starting something that will develop the sport and the country.

New Zealand has announced it is tightening rules surrounding foreign trusts after numerous documents in the Panama Papers leak referenced the country.

Officials in Wellington said the changes would improve the disclosure and registration of foreign trusts, as well as strengthening anti-money laundering rules.

"The changes to the foreign trust rules are a matter that the Government intends to move quickly on," Finance Minister Bill English said.

In the TV3 Reid-Research poll - released last night - Kiwis were asked whether they wanted change now that they had seen the final four alternative flag options.

Only 25 percent said yes, while the majority said no.

But PM Key - who has previously voiced his support for the silver fern on the flag - said the question asked was too basic, as there were people who had yet to make up their minds.

He told Morning Report fewer than 50 percent of people want to keep the current flag, and that number was falling.

John Key is attending the Forum leaders meeting in Port Moresby which opened last night.

The meeting was preceded by declarations by Small Islands States, NGOs and Fiji's Pacific Islands Development Forum calling for greater action including no more than a 1.5 degree rise in global temperature above pre-industrial levels.

Developed nations have traditionally looked at two degrees as a more realistic target.

Mr Key says he is happy with the work New Zealand has done to fight climate change.