New Zealand's Prime Minister John Key addresses the audience during a meeting at the APEC (Asia-Pacific Economic Cooperation) Ceo Summit in Lima, Peru, November 19, 2016. [Photo/Agencies]

WELLINGTON -- New Zealand Prime Minister John Key on Monday shocked the nation and his cabinet by announcing his resignation after eight years at the head of one of the most popular governments in the country's recent history.

Key, who led his center-right National Party to three successive general election victories, said in a broadcast statement that he would not lead his party into a fourth term in next year's election.

His voice audibly shaking, Key said he had informed the cabinet the same morning.

"I do not believe that, if you asked me if I was committed to serving out a fourth term, that I could look the public in the eye and say yes," he said.

"This has been the hardest decision I have ever made and I do not know what I will do next. But for me this feels the right time to go."

He cited family reasons for his resignation, saying the post had required great sacrifices "from those who are dearest to me."

"For my wife Bronagh, there have been many nights and weekends spent alone, many occasions that were important to her that I simply could not attend," said Key.

"My daughter Stephie and my son Max have transitioned from teenagers to young adults while coping with an extraordinary level of intrusion and pressure because of their father's job."

Key said the National Party Members of Parliament would hold a special caucus on Dec. 12 to choose a new leader, who would have time to "settle in" before the next election.

He was confident his party would be returned to power in the election which must be held by November next year.

Key, who was elected to parliament in 2006, said he would not be contesting his parliamentary seat of Helensville, in the mainly rural northwest of Auckland, at the next election.

He said the caucus had "a number of individuals who would make a fine future PM," but he would support Deputy Prime Minister and Finance Minister Bill English in the leadership race, if English put himself forward.

"Whoever the caucus elects will have my unwavering support, but if Bill English puts his name forward then I will vote for him," said Key.

"For 10 years now Bill and I have worked as a team. I have witnessed first-hand his leadership style, his capacity for work, his grasp of the economy, his commitment to change and, most of all, his decency as a husband, as a father, as a friend, a colleague and as a politician."