Labour leader David Shearer says insults such as those John Tamihere has handed out in the past few days would be unacceptable from a member of his caucus.
However, he would not say whether Mr Tamihere was unsuitable to be a Labour candidate, saying it was part of the "shock jock" nature of Mr Tamihere's radio job.
On Radio Live yesterday, Mr Tamihere called 3 News reporter Tova O'Brien a "stupid little girl" after she asked him whether he was a misogynist, homophobe or sexist.
He also described Social Development minister Paula Bennett as "that bloody fat girl" to the Herald on Sunday - the day after Labour accepted him back into the fold as a party member.
Asked if such comments would be acceptable from one of his current MPs, Mr Shearer said "of course it wouldn't be".
"He's not a member of my caucus, and that would be unacceptable."
He said it was up to the party itself to decide whether to sanction Mr Tamihere over such behaviour.
"I am responsible for my MPs, but not every member of the party."
Mr Tamihere has expressed an interest in becoming an MP again and Mr Shearer said Mr Tamihere would "have to front up and explain himself" if that was to happen.
However, he would not be drawn on whether Mr Tamihere was suitable to stand for Labour, saying that would be decided during party selection processes.
"I don't agree with John Tamihere in many of his comments - but he is also a shock jock, this is what he does for a living. That doesn't excuse what he said, but that is, in some sense, what he is paid to do."
He would not say whether he believed Mr Tamihere should be an MP again, saying the best person for the job would be selected through Labour's selection processes.
In accepting Mr Tamihere as a member again, Labour Party president Moira Coatsworth said Mr Tamihere was subject to the rules and Constitution of the party.By Claire Trevett @CTrevettNZH Email Claire