Labour leader David Shearer insisted he had the confidence of his caucus following a hostile party conference.
Conference delegates voted in favour of a proposal that enables a leadership run off to be triggered by fewer than half of the MPs in caucus.
This was a significant win for supporters of David Cunliffe as Labour leader, but Shearer insisted afterwards he had the party's backing.
"I have absolute confidence, I can tell you quite assuredly, I will be the leader in 2014 that takes Labour into government."
Asked if he believed Cunliffe had been disloyal, Shearer would not answer directly.
"He gave me his loyalty last week... I can only take him on his word."
The proposal voted for by the delegates was:"The number of votes required to endorse the leaders shall be 60 per cent of votes cast plus one. If the party leader is not endorsed, a leadership election process is triggered."
The vote would take place every three years within three months of an election.
There would then be a vote which would give the membership a say of 40 per cent, unions and affiliates 20 per cent, and MPs 40 per cent. Currently only MPs can vote for the leader.
There were huge cheers and gasps of surprise when a vote saw the amendment passed. The vote was 264 for and 237 against.
The vote is seen as boosting Cunliffe's chances of seizing the leadership, and suggests a split between the MPs and the wider party membership.
It indicates Cunliffe is supported by a majority of the grassroots, despite not having enough support in the caucus to force a leadership change.
FOR AND AGAINST
A succession of MPs and delegates stood to speak for and against the proposal, which follows the presidential style run off last year in which Shearer was elected leader by the party's 34 MPs.
Joining the lineup of speakers was Rimutaka MP Chris Hipkins, who urged the party to vote down the proposal, which he slated as undemocratic.
But MPs Lianne Dalziel and Louisa Wall were in the opposite camp, and urged delegates to support the change.
MP and former Labour Party President Andrew Little urged delegates to vote down the proposal and acknowledged that it was aimed squarely at Shearer.
"Let's call it what it is," Little told conference delegates.
"[It's] contemporary anxiety about the leadership."
But as one party member after another got up to speak, it became clear that the membership were feeling increasingly disenfranchised from the party's MPs.
'Today is the day the membership takes the party back," was the rallying cry from one delegate.
Those on the losing side, who argued for a 50 per cent trigger, said their way was more democratic.
They said the winning proposal would create huge uncertainty and make it more difficult for Labour to win an election.
This was because an election winning Labour prime minister would have to face a leadership challenge from within the party just three months after taking office.
Former party secretary Mike Smith said the 40 per cent trigger gave "a minority a higher right".
But former party secretary Chris Flatt, now with the dairy workers union, said the leader would still need a majority.
"This is merely the trigger (for a vote). I don't think there will be a stability message."
He said it would be a great message when leader David Shearer got the backing of more than 60 per cent of the caucus and could tell the media that.
Carmel Sepuloni, who narrowly lost to Paula Bennett in the Waitakere seat, said 34 MPs were not a majority of the party.
Whangarei delegate Pat Newman said: "If you can't come up with 60 per cent and the shenanigans don't stop... then we need to step in."
A delegate from the Christchurch suburb of Woolston said in combination with a later remit, the 40 per cent trigger was aimed at destabilising the party "so there is a vote in February that will be difficult for the current leadership to pass".
The caucus is due to vote on the leadership next in February.
Shearer has refused to say where he stood on the vote, because he had a conflict of interest, but Cunliffe voted in favour of a 40 per cent trigger.
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