Mr Shearer, who appeared TVNZ's Q+A this morning following Labour's successful Ikaroa-Rawhiti by-election result, was quizzed about the allegations and reports of a possible party leadership challenge.
"I'd like to know who the MP is," Mr Shearer said in reference to reports some MPs had told media their could be a challenge to his leadership within two months due to poor polling results.
The latest Herald-DigiPoll survey showed support for Labour and Mr Shearer had slumped.
Mr Shearer had dropped 6.1 points as preferred Prime Minister in this week's survey, while his party slid 6.6 per centage points to 30.9 per cent overall.
The last survey was carried out in March.
Mr Shearer this morning confirmed he had the full support of his party.
"I haven't heard any of this before," he replied when questioned about the possibility of division among his MPs.
"Polls go up and down," he added.
He also appeared on a special edition of TV3's The Nation and said: "I've asked my colleagues and they haven't heard anything about it [leadership challenge]".
"I can't comment any further when I don't know who this person is."
