Labour leader David Cunliffe says Justice Minister Judith Collins is a trout.
She responded by calling him a "recidivist sexist", as he previously said the human race would die out if she was the last woman on Earth.
Mr Cunliffe made his comment in a blog post on the website The Ruminator yesterday.
He said: "The original brief was to respond to a post by Judith Collins. My post was going to be about snapper, not trout. But considering that issue, along with Judith's leadership aspirations, has floundered, I'll try another hook."
Asked to respond on Twitter, Ms Collins tweeted: "Imagine the outcry from Labour if one of Nat male MPs called a Labour woman a trout."