Over the past week, Labour MP Su'a William Sio has said he believed that his colleague Louisa Wall's bill to legalise same-sex marriage could cost Labour the election and called for it to be withdrawn.
There have also been reports by TV3's political editor Duncan Garner that senior Labour sources had told him Labour MP David Cunliffe was not trusted, widely disliked and that Mr Shearer was regretting his decision to keep him on the front bench - something Mr Shearer has denied.
Clearly frustrated, Mr Shearer said he would tell his caucus that they must only talk about their portfolio areas and could not publicly discuss the Labour Party as a whole.
"They are going to be getting rev-up today. I will be giving them a very unequivocal, clear steer today that 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."
Asked about Mr Sio's comments, he 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."
"That is the message I will be taking to the caucus today and they will be left with absolutely no doubt in their minds about what I mean in terms of keeping the messages relevant to their portfolios."
He denied he was gagging his MPs, saying they were able to speak freely on matters within their portfolio and constituency issues.
Mr Shearer said Mr Sio had spoken out of turn, and had since apologised to him. Asked if he had control of his caucus, Mr Shearer said "absolutely."
He said he had spoken to Mr Cunliffe over the weekend, but it was a private conversation. He said he trusted Mr Cunliffe, and described him as smart and a valuable member of the front bench.
Mr Cunliffe has just returned from an overseas trip. When asked about the suggestion some of his colleagues were starting a travel fund to keep him away from New Zealand Mr Cunliffe said : "Well I'm back and I'm refreshed and I'm ready to take the fight to the Government with our team."
Mr Sio would not comment this morning.
Mr Shearer said he "absolutely" believed he would still be the party leader in 2014.
However, Mr Shearer could find himself on the receiving end of some criticism as well, for a Grey Power speech in which he used the example of a sickness beneficiary working on his own roof to say he did not support benefit fraudsters.
Labour caucus sources said Mr Shearer was expected to be asked about the comments, which prompted an angry reaction from some party members on Mr Shearer's Facebook page.
Mr Shearer said he did not resile from that speech:
"I was talking about fairness, and fairness is a very important issue for New Zealanders; whether you are a millionaire not contributing or somebody who is on benefit who shouldn't be on one. New Zealanders expect people to pull their weight."
Among those who complained was Joan Caulfield, former Prime Minister Helen Clark's long-serving electorate secretary, who posted on Mr Shearer's Facebook page that the dig at sickness beneficiaries was a "cheap shot" she would expect from a National Party MP.
"Do you know what his illness is? Maybe he has a mental illness and cannot hold down a job. Passing the test set by Work and Income is very difficult and requires a medical certificate. Sickness beneficiaries I know live in poverty and need support from families to survive," Ms Caulfield said on Facebook.
- By Claire Trevett and Kate Shuttleworth
