Asked if she believed there was a perception she had underperformed, she said nobody had raised concerns with her about it.
"I can't think why, and if that is the case, it's the first I've heard about it."
Mr Shearer has refused to comment on his specific plans for the reshuffle. Asked about Ms Mahuta's comments, he said he made it clear from the start that all portfolios would be reviewed after a year "and that's what I'll do."
Asked about her future in politics, Ms Mahuta said she did intend to stand again in 2014. She was more dismissive about the possibility John Tamihere could run for Parliament again, saying Labour had decided during its recent organisational review that it should focus on attracting more young people and women to ensure it was in a strong place through to 2026.
"John Tamihere says a lot of things, and a lot of them are very memorable, like front bottoms, so if there's space for John Tamihere in the Labour caucus it will probably be at the call of the current leadership. But what I know is that the future of the Labour Party will require looking to a younger generation of Maori leadership."
Mr Tamihere is understood to be considering a return - and will not rule it out. However, he is no longer a party member and has not yet applied to rejoin the party - something which will require approval from the party's General Secretary Tim Barnett. It is very rare for a membership to be blocked, but high profile applications are considered carefully, including any previous criticisms of the party.
Shane Jones and Parekura Horomia are yet to commit to standing again, and Ms Mahuta said Labour's leadership needed to ensure strong Maori and Pacific representation for the future.