WELLINGTON • New Zealand's socially conservative finance chief Bill English has been sworn in as Prime Minister, following last week's shock resignation of his popular predecessor, Mr John Key.

The centre-right National Party caucus unanimously backed Mr English at a meeting yesterday.

The 54-year-old said he was "excited and humbled" to take the top job after eight years as Mr Key's deputy and finance minister. His challenge will be to win over a public shocked by Mr Key's departure and keep the party riding high in the polls as it attempts to win a fourth straight election late next year.

A former farmer with degrees in commerce and literature, Mr English was National's leader when it suffered its worst election defeat in 2002. "You learn more from losing than you do from winning," he said.

He was Mr Key's preferred successor after returning the budget to surplus and keeping the economy at about 3 per cent growth. He has overseen deep reforms of the public service aimed at improving social outcomes and reducing costs.

He said New Zealand's prosperity means it has no pool of disaffected voters responsible for Britain's Brexit and US President-elect Donald Trump's victory. He added that a priority for his government was ensuring that the most needy people were given opportunities.

"We have a strong economy, almost unique in the developed world, and most New Zealanders would expect to be able to share in that," he said.

A staunch Catholic with six children, Mr English is regarded as far more socially conservative than Mr Key.

State Services Minister Paula Bennett, 47, was named deputy leader.

AGENCE FRANCE-PRESSE, BLOOMBERG