National's Alfred Ngaro has posted a video pretending to outlift Labour's Stuart Nash, using tiny weights.
It follows Mr Nash, a Minister of the Crown, posting a video on Tuesday evening of himself lifting weights in the Parliamentary gym.
He said he did five sets of 12 reps with 45kg dumbbells, subtly pointing out that there were no heavier weights available in the gym.
"Not bad for an old geezer," he said.
The video was filmed at 11pm in between reading papers, Mr Nash said on the video posted to his Facebook page.
Mr Ngaro has responded to the video with one of his own.
"Hey Stuart Nash - you've inspired me! Saw your video last night and thought I'd give it a go in the gym this morning. 3 sets of 1 rep with 1kg - boom! What do you think of my form Nashy? " he said.