(CNN) Bill English has been sworn in as the next Prime Minister of New Zealand.

English was elected as the leader of the National Party, replacing former Prime Minister John Key.

Key unexpectedly resigned on December 5 after leading his party for 10 years and the country for eight.

"I am both excited and humbled by this opportunity," English said in a statement. "As Prime Minister, I will be committed to building a New Zealand which rewards hard work and enterprise and which cares for our most vulnerable."

English previously led the National Party to its worst-ever electoral defeat in the 2002 election. He has served as deputy prime minister and finance minister.

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