Labour's caucus met this morning and its former leader David Cunliffe resigned while David Parker was elevated from deputy leader to acting leader with Annette King as his deputy.
They will hold the roles until Labour holds its leadership contest. Many MPs wanted the review done first, but Mr Parker said waiting until December 7 was too long without resolving the leadership.
However, it was hoped the timing would allow for an interim report to be made by the review team.
Mr Parker played down the ructions between Mr Cunliffe and Mr Robertson and said the same code of conduct would apply to the contestants as in the last contest. The message from caucus to the contestants was to "be responsible".
"You can't have a contest without people robustly exchanging views, but I hope we'll keep it seemly."
Mr Cunliffe's resignation means he no longer has the resources of the leaders' office at his disposal to help in his re-election campaign - although he got in a last ride in the Crown BMW to Parliament this morning and his chief press secretary was by his side on the way into caucus.
Ms King denied it was the most torrid time faced by Labour in her experience.
"The 1980s were much worse," she said.
"Whenever there is a loss by a party there is going to be a time of turbulence. I have to say I've been there and seen that before. We will get through it, and we will come out of it and will be a strong party. This isn't a permanent position."
Mr Parker said he and Ms King - "the grandmother of the party now" - were chosen because they could offer stability and impartiality in the interim.
He has ruled out entering the leadership contest himself, but would not deny some MPs had asked him to stand because of concerns some had with both Mr Cunliffe and Mr Robertson.
"I made a decision last week that I wasn't going to stand and I haven't changed that position. I'm sure just about everyone in that room has been asked by someone to stand as leader. We've all got our supporters."
He said he was not aware of any other MPs who intended to stand, but nominations had not yet been called.
Mr Parker has said he has lost confidence in Mr Cunliffe but would not expressly endorse Mr Robertson. Ms King would not say who she would support.
Asked if Prime Minister John Key should be worried about facing the interim partnership of Mr Parker and Ms King, when Parliament reconvenes next month, Mr Parker laughed and said, "I don't think so".
"We are the same people we were before the election, sadly, because we haven't bought many new people into Parliament," he said.
"We will regroup. We are behind some of the most important social and economic changes New Zealand has seen in the last 90 years and we will be that force again in the future."
He said he was sure Labour would be the butt of jokes from National, as National had been after its 2002 defeat.
"We're pretty practised at it so we're getting better at dealing with it."
Ms King said neither she nor Mr Parker were shrinking violets and they would take Mr Key on in Parliament.
Mr Cunliffe has compared his election loss to former Labour PM Norm Kirk, who survived two defeats to go on to be leader. Ms King said she could not say if it was similar.
"I might be old but I'm not that old. It's up to him who he compares himself to."
- by Claire Trevett, Isaac Davison
