Labour's acting leader David Parker says he did not intend to seek the leadership when he took on the acting role two weeks ago.
Mr Parker, who is Labour's finance today announced he would seek the leadership, going up against David Cunliffe, Grant Robertson and Andrew Little, while David Shearer is also considering a bid.
He made the formal announcement at a press conference at 2pm in Auckland.
Mr Parker said he genuinely did not intend to seek the leadership when he took on the acting role after the resignation of David Cunliffe.
"However, over the past ten days I have been approached by many people from all walks of life, across the spectrum, asking me to stand. The main thing people have said to me, even people who did not vote Labour this time, is that this country needs a strong and viable Labour Party."
Mr Parker conceded the party's tax policy scared some voters at last month's election.
He said he was committed to reviewing all policy and to looking for solutions.
"But I will not throw away my desire to solve the problems they were designed to fix - leadership is more than just being populist," he said.
Mr Parker said it was up to Labour's caucus whether he stayed acting leader during the leadership election campaign.
Mr Parker will be going up against his former leader, Mr Cunliffe, Wellington Central MP Grant Robertson and former union leader and ex-party president Andrew Little.
Mr Little has said he would ditch some of Labour's less popular financial policies championed by Mr Parker, including a capital gains tax and raising the pension age.
Meanwhile the former Labour leader, David Shearer, has indicated he is still considering another tilt.
Nominations close on Tuesday and the new leader will be announced on 18 November.