Labour MP David Cunliffe has returned from overseas to face claims made by anonymous colleagues that he was widely disliked and not trusted, saying they were "clearly unwarranted, uncalled for and untrue".
Mr Cunliffe also said he supported Labour leader David Shearer, who yesterday hauled his caucus over the coals for the comments about Mr Cunliffe and other "sideshows".
There has been ongoing speculation about Mr Cunliffe's ambition since he was defeated by Mr Shearer in the leadership contest last December - and a change in the party rules to allow trade union and party members a vote on the leadership has reignited it.
Asked about Mr Shearer's leadership, Mr Cunliffe said he was "very supportive of it".
"And any suggestion to the contrary is just nonsense. I think he's going to be a great Prime Minister and he's a good guy."
Mr Shearer yesterday laid down the law to his caucus, telling them to stop getting caught up in "sideshows" after a recess week of ill-discipline and renewed discussion about his leadership.
The past week included criticism of Labour MP David Cunliffe by anonymous Labour MPs to TV3 political editor Duncan Garner, who blogged that Mr Cunliffe was widely disliked and was not trusted by Mr Shearer. In a separate incident, MP Su'a William Sio claimed his colleague Louisa Wall's bill to legalise same-sex marriage could cost Labour the election.
It coincided with two further polls showing Labour had slipped slightly in support - prompting a further round of discussion about his leadership from the party's wider membership.
Mr Shearer said the incidents were a distraction and he had given caucus a "rev-up", telling them he expected only to see public comments about their portfolio areas.
"I want them to focus on the areas that are of most concern to New Zealand. I do not want them to be focusing on side issues. My message was heard and understood."
Asked about Mr Sio's comments, Mr Shearer said people were entitled to their opinions on gay marriage "but I don't want him talking about general Labour issues, that concern the Labour Party".
He denied he was gagging his MPs, saying they were able to speak freely on matters within their portfolio and constituency issues.
Labour MPs were also told off by former party organiser Jenny Michie who wrote on the Standard blog that they needed to "get it together". She said the comments about Mr Cunliffe were the last straw and MPs could not afford to indulge in "disloyal, backstabbing" behaviour or they would alienate not only the public but also party activists.
Mr Shearer said he believed he had control over his caucus and his leadership was safe until 2014, although Labour could be doing better in the polls. However, he did not believe that he was not connecting with the voters.
Labour's troubles provided further fuel for National - State Services Minister Jonathan Coleman said in Parliament that Mr Cunliffe's return "meant trouble". "It means more self-hatred and tearing each other apart and that is great news for the Government, so welcome back."
Mr Shearer was also expected to be criticised - it is understood some caucus members were upset about Mr Shearer using the example of a person on the sickness benefit to state he did not approve of welfare fraud. Mr Shearer used the anecdote in a speech to GreyPower last week and yesterday said he stood by it.