New Zealand’s Prime Minister John Key surprised his country today by announcing his resignation after eight years as PM.

He announced his decision at a Monday press briefing and said he would back his deputy Bill English as the new leader.

Mr Key said he did not want to contest a fourth general election next year and he thought it was best to leave now while he was on top.

He spoke of the personal sacrifices he had made for the job and said the role had taken a toll on his wife, Bronagh, and family.

New Zealand's National Party caucus is to meet on December 12 to decide on a new party leader and prime minister.

According to reports, the New Zealand dollar fell by nearly 1 percent on the news and was trading at $0.71 U.S.

Mr Key was a currency dealer before he entered parliament, becoming leader of his center-right opposition party in 2006 and then winning his first general election to become prime minister in 2008.

He went on to win elections in 2011 and 2014 and enjoyed high popularity ratings.

 “...despite the amazing career I have had in politics, I have never seen myself as a career politician. I have certainly never wanted my success in politics to be measured by how long I spent in Parliament,” he said today

“All I can say is that I gave it everything I had,” he said. “I have left nothing in the tank.&rdquo.