"This is not to say that some of the people we have sent offshore haven't been the best choice, or not done excellent service, but some have not been the wisest choice.
"Many have represented an insult to foreign affairs, leaving their posts with absolutely nothing to show, but deterioration in our international relationship with that country."
Mr Peters went on to say that a political appointee should be "the absolute exception", and if any future appointments were made that the party regards as unsuitable, it would order that appointee home should it hold the balance of power after next year's election.
NZ First members have recently been ordered out of Parliament after objecting to the rulings of Mr Carter, a former Cabinet minister and National MP.
Mr Peters also had a fractious relationship with former Speaker Lockwood Smith. In 2012, he objected to Dr Smith's appointment as High Commissioner in London, saying it should be the last time someone is appointed Speaker with the promise of being given a plum diplomatic post.
It is an old grudge, dating back to the days when Dr Smith won National's selection for the Kaipara electorate over Mr Peters.
In 2012 Mr Peters also put in a no-confidence motion against Dr Smith, after the NZ First leader was ordered from the debating chamber when he tried to raise a point of order.