National's Alfred Ngaro's burn on Police Minister Stuart Nash's gym brag

National MP Alfred Ngaro has delivered a good old-fashioned slap down after Police Minister Stuart Nash posted a video of himself pumping 45kg dumbbells at the Parliamentary gym.

"What (a couple) of MPs get up to in parliament at 11.00pm in between reading papers.

"5 sets of 12 reps with 45kg dumbbells (no heavier weights available in Parliamentary gym). Not bad for an old geezer," Nash bragged on Facebook.

As he finished his set and sat up to look at the camera, a red-faced Nash said "there you go, mate. Do that one."

That caught the attention of fellow gym goer Ngaro, who has guns of steel but was clearly unimpressed with Nash's late-night gym braggadocio.

He quickly issued a response on his own Facebook page - pumping 1kg weights complete with much faux huffing and puffing and eye popping to the soundtrack of cameraman Northland MP Matt King laughing.