"I was not the person who could bring that caucus together, so whether I could win the primary was not the issue. I am not intending to run for the leadership again."
Mr Cunliffe also returned fire against former party leader David Shearer, who had called on him to leave politics altogether because of the risk he would undermine the next leader. Mr Shearer has accused Mr Cunliffe of undermining both himself and Phil Goff when he was leader, which Mr Cunliffe rejected.
"There was no truth to the allegations Mr Shearer made. They were unfortunate and a breach of caucus discipline. I wish him well in whatever he decides to do, but I have never undermined David Shearer and had nothing to do with his demise [as leader]."
Mr Shearer said he stood by everything he had said about Mr Cunliffe "but I'm not going to engage in any more comments, as we agreed at the last caucus".
Asked about former Australian Prime Minister Julia Gillard's comment that failed leaders should leave politics, Mr Cunliffe said if people were calling for that from him "perhaps they ought to do that in order of succession ... there are two others ahead of me".