The center-right National Party caucus unanimously backed English at a meeting on the morning of Dec. 12 and he travelled to Government House in Wellington a few hours later to officially take over.
State Services Minister Paula Bennett was named as deputy leader.
English, 54, said he was “excited and humbled” to take the top job after eight years as Key’s deputy and finance minister.
“This will be a government supporting economic growth and ensuring that the benefits of growth are widely shared,” he told reporters.
National Party president Peter Goodfellow said English and Bennett offered “a good mixture of experience and fresh thinking.”
“Under their leadership, New Zealanders will continue to benefit from the stable government they expect, along with a dedicated focus on delivering results for families and businesses,” he said.
A former farmer with degrees in commerce and literature, English has been in parliament since 1990 and was previously leader of the National Party in 2002 when it suffered its worst election defeat.
“You learn more from losing than you do from winning,” said English, who will seek National’s fourth straight election win in late 2017.
He was Key’s preferred successor after returning New Zealand’s budget to surplus and keeping the economy ticking over at about three percent.
English said New Zealand’s prosperity meant the country did not have the pool of disaffected voters responsible for Brexit and U.S. President-elect Donald Trump’s victory.
And he said a priority for his government was ensuring the most needy 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 committed Catholic with six children, English is regarded as far more socially conservative than Key, opposing the 2013 legalization of same-sex marriage and speaking out against abortion and voluntary euthanasia.