Helen Clark's decision to stand down caught senior Labour MP Peter Hodgson by surprise.
The Dunedin North MP, who retained his seat, said he had not expected her to stand down straight away. He had expected it would be in a couple of months "or even longer."
But Mr Hodgson said the move was also typical of Miss Clark's decisive nature
Miss Clark announced her decision to stand down as Labour Party leader after conceding defeat to John Key.
"My job as leader of the Labour party is complete," she said, announcing her resignation as leader.
"I'll be standing down and expecting Labour Party colleagues to elect a new leader by Christmas."
Miss Clark talked of her pride in leading Labour back to "electoral respectability", and winning three elections.
"I'll be looking back on these last nine years with an incredible amount of pride."
Miss Clark said she would stay on as the MP for Mt Albert.
