Mr Shearer said he would have preferred it for the new leader's sake if Mr Cunliffe had stayed in the race and lost. "I think it would have been easier for whoever wins if he had stood and lost. It would be a cleaner break for whoever takes over. His followers undermined Phil Goff and myself and I think he continues to be a presence that will make it difficult for a new leader."
He said if Mr Cunliffe had lost this would have sent a clear message to his supporters, rather than let them have the impression he could have won if he hadn't withdrawn. He was also disappointed with Mr Cunliffe's decision to stay on as an MP. "It would be easier for the new leader if he decided to move on."
It was a sentiment echoed by several other MPs, although none would be named.
Mr Cunliffe pointed out Mr Shearer was also a former leader.
"I think that's an unfortunate thing for him to say and it belies my long-term loyalty to the party and caucus."
Mr Shearer has been criticised for making the comments, but denied he spoke out to get "revenge".
"It's about making sure we set ourselves up for the future so the new leader doesn't have the same experience I had."
He had been white-anted by Cunliffe's supporters when he was leader and did not want the same thing to happen to the new leader.
Mr Cunliffe and some of his supporters, including Sue Moroney, have said they believed he still would have won the leadership if he had not withdrawn.
Mr Shearer said he did not believe that, but it would have been better for Mr Cunliffe to have stayed in the contest to put to bed that question once and for all.
"Many of his supporters believe he is the True Leader. And I don't believe their ambitions for him will die. They were the people who gave me a pretty difficult time. We could have had a fair contest and whatever happened we would have had a clean line underneath it."
He did not believe he was making matters worse by speaking out.
"What happened to me should not happen to the new leader. We need to give the new leader every chance they can get, chances that Phil Goff and I perhaps didn't have.""
Mr Shearer was also criticised by Cunliffe loyalist Greg Presland on the Standard blog.
Writing under his pseudonym Mickey Savage, Mr Presland said Mr Shearer was simply feeding a "right wing narrative."
"And attacking David Cunliffe and then saying that the attacks need to stop brings to mind a word that starts with "h". I agree with the sentiment that Caucus needs to unite and move on. Note to David Shearer, please do this."
However Mr Shearer said he had been subjected to "undermining and white-anting" by Mr Cunliffe's supporters when he was leader and did not want that to be experienced by the next leader.
"You've got to ask him what his intentions are now. If he wants to stay then what we would want is absolutely for him to get behind the new leader."
He said he would like to think Mr Cunliffe could be trusted "but that's up to him."
Labour MP Clayton Cosgrove pitched in to back Mr Shearer, saying Mr Presland's post this morning only went to prove Mr Shearer's point.
The Standard's Lyn Prentice also recently took down a post criticising Mr Cosgrove at the request of Labour's General Secretary Tim Barnett but has said it would go up again after the leadership contest.
Labour leader aspirant Andrew Little said David Cunliffe's endorsement of him "cuts both ways" and he was not relying on it to win the leadership.
"David still commands a fair amount of respect in some quarters of the party and so it helps in that regard. There are others who don't hold David in as high regard. I am very clear that I am running this race on my mettle and what I have to offer. It's going to be my effort that goes into this race as we get into it."
Asked if he agreed with David Shearer that it might be better for Mr Cunliffe to leave Parliament altogether, Mr Little said that was up to Mr Cunliffe.
"He's had a go in the leadership role, he stepped out of it. I don't think he's going to be going back into it. What David decides to do with the rest of his Parliamentary career is up to him."
However, he would not condemn Mr Shearer for speaking out saying the caucus and party were "in a state of flux" at the moment but everybody knew they had to pull things together by 2017.
"David Shearer is doing that, we're all doing that. I'm not particularly fussed by his comments but we all know that success is dependent on everybody sharing the job and sticking to the common cause we all share."
He said he had made no promises or pledges to any of his colleagues, including Mr Cunliffe.
Mr Little has indicated he will consider having a woman as his deputy, but such decisions would not be made until after the leadership was resolved.
"I think we need to have a front bench that is reflective and representative of New Zealand. There are no promises, no pledges, no nothings."
Louisa Wall and Sue Moroney both said they would consult with their local members before deciding who to back now that Mr Cunliffe had withdrawn.
Ms Wall said she had intended to back Cunliffe and was lined up to be one of his nominees before he pulled out.
Asked about the deputy role: "If one of the candidates wants to run on an equity ticket, why not?"
Meanwhile, Service and Food Workers Union representative Jill Ovens said many of its members were still firm Cunliffe supporters and would be disappointed he had withdrawn. She said his nod to Mr Little would be valuable. "But I don't think any of the three can take for granted the support of party or union members."
Mr Little said Mr Cunliffe had spoken to him before making his decision and had indicated which areas he would like to be involved in. But Mr Little said he had not asked for Mr Cunliffe's endorsement and would not be offering any positions before the leadership vote.
Both Mr Parker and Mr Robertson said they welcomed Mr Cunliffe's decision to pull out, describing it as for the good of the party. They said it was up to him whether he stayed in Parliament or not.
Mr Shearer would not say who he was likely to back. He said it had been a hard decision not to run for the leadership because he felt he had unresolved business. He did not intend to quit.
"I have no plans of leaving. I want to help in rebuilding."
He told Radio New Zealand today the Labour Party had three years to rebuild and get in behind the new leader.
"I believe that what we need to make sure is that we have the ability for the Labour Party to go forward behind the new leader, without any murmur or dissent.
"The people who had attacked himself and Mr Goff were mostly anonymous, Mr Shearer said.
"There are certainly some who's names I think I know, but these are people who sit behind darkened screens and blog and undermine people.
"What we don't need is that. Let's have a clean start, let's move on behind the new leader."
The party was not meeting the aspirations of the "people in the middle", he said.
"Those are the people who work in offices, the contractors, the self-employed people who are working really hard and trying to get ahead and we're not standing up for those people
"There's a real brand issue for Labour I believe."
Mr Parker said Mr Cunliffe had made "the right decision" in pulling out of the leadership contest.
Meanwhile, commenting on rival leadership contender Andrew Little's suggestion that Labour's deputy leader should be a woman, Mr Parker said he would instead support the most suitable candidate for that role if gained the leadership.
"I will be going for competence in every position I appoint whether it's deputy or anyone else and I would note that I think Helen Clark would be horribly offended to think that she achieved the position of being one of the best prime ministers we've had in New Zealand on the basis of her gender.
"Gender is relevant but competence trumps everything."
He also said Mr Cunliffe's suggestion of a new co-deputy leader structure with one of those two roles being earmarked for a Maori caucus member was "a fruity idea and I oppose it".
"I just don't think having co-deputy leaderships washes. You've got to take decisions on the basis of competence. Let's not faff around."
The Labour caucus decided today that David Parker would remain acting leader during the leadership contest.
Mr Parker said Mr Robertson and Mr Little, his leadership rivals, did not believe he would be given an unfair advantage by remaining in the position.
Speaking after the caucus meeting today, Mr Parker said: "I don't want to be seen to be taking advantage of my position.
"I would have been happy with either outcome and both Grant and Andrew made the point that it's probably better for the party if I stay in the role."
Acting deputy leader Annette King would take over the day-to-day duties such as media interviews and leading Labour in the House.
The three confirmed leadership candidates will be on the hustings when Parliament resumes next week, and were unlikely to play in part in Question Time.
Mr Parker also revealed the two MPs who nominated him for leadership - Manukau East MP Jenny Salesa and West Coast MP Damien O'Connor.
- Additional reporting APNZ staff, Adam Bennett, Isaac Davison
