Labour MP David Shearer is set to be censured for breaking the Labour line on the Trans-Pacific Partnership after speaking out in support of the trade agreement.
Labour leader Andrew Little would not outline possible sanctions or comment on whether Mr Shearer could be stripped of his foreign affairs portfolio.
"There is a range of options. I don't want to go into any of them, but it is important he understands, and that every caucus member understands, that caucus collective responsibility is real and it's got to stand for something."
It follows comments Mr Shearer made to the Herald in support of the TPP, just days after Labour's caucus had decided it would oppose any legislation required for the TPP. The sanctions could depend on Mr Shearer's willingness to back down from his stance and are likely to range from a reprimand and apology to being stripped of his portfolio and demoted. As foreign affairs spokesman, Mr Shearer sits on the foreign affairs select committee which will be considering the TPP.
Although fellow MP Phil Goff also spoke in support of the TPP, Mr Little said he had agreed Mr Goff could break ranks with the party because of his long-standing support for the trade agreement as Trade Minister when the talks kicked off.