NZME understood that Key's wife Bronagh asked him to resign.
The National Party caucus will hold a meeting on December 12 to decide the new party leader and Prime Minister.
Key cancelled his weekly scheduled interview with NewstalkZB at the NZME offices in Auckland this morning, and instead was interviewed over the phone from Wellington.
Key has led the National party since 2006.
Key built a career in foreign exchange in New Zealand before continued success in the industry overseas.
He entered Parliament in 2002 as National's representative for Helensville. In 2004 he was appointed Finance Spokesman for the party and succeeded Don Brash as party leader in 2006.
Key led his party to win the election in November 2008 and repeated the victory in 2011 and 2014.
Key has governed the country through the recession of the late-2000s, formed the Canterbury Earthquake Recovery Authority in response to the aftermath of the 2011 Christchurch Earthquake and created a much-protested policy for the partial privitisation of five state-owned enterprises.
Key has also withdrawn the NZ Defence Force from Afghanistan and worked to establish the TPP with the United States.
- NZ Herald
