Prime Minister John Key resigns after eight years in power, calling it the hardest decision he has ever made.

New Zealand Prime Minister John Key unexpectedly announced his resignation on Monday, saying it was the “right time” to leave politics after more than eight years in power.

Key said he had no immediate future plans, but told reporters he would stay in parliament long enough to avoid a by-election for his seat.

“There is no way I could have served out a full fourth term,” Key said at his weekly press conference in Wellington, citing family reasons for his departure. “I think in reality if I served six months or a full-year, I would have inevitably had to look down the barrel of a camera and say ‘I will serve a full three years.’ I would therefore have mislead the public and that is not the way of operating.”

The former Merrill Lynch currency trader called it “the hardest decision I’ve ever made”, with no plans on what to do next other than spend more time with his family.

Key recently marked his eighth anniversary as prime minister and 10th year as leader of the centre-right National Party, which is set to meet next week to elect his successor. His deputy Bill English is widely seen as favourite to take over.

Bill English, deputy prime minister and finance minister, said he would likely decide overnight whether to stand for the leadership of the ruling center-right National Party at a special December 12 caucus meeting.