Stupid little girl.

Of all the put-downs Parliament's debating chamber has given us, that must be one of the most offensive.

It's sparked something of a rebellion in Parliament, that phrase.

Speaker Trevor Mallard says he heard someone from National's side of the debating chamber use it to describe Prime Minister Jacinda Ardern. Mallard says he heard a man's voice, coming from somewhere behind leader Simon Bridges' seat.

But National says it never happened. Bridges reckons no one said it and no one other than Mallard appears to have heard it.

We'll never know for sure. Parliament's microphones didn't pick up the comment clearly enough to prove or disprove the allegation.

Still, whether National said it or not, they certainly rubbed it in. And appeared to revel in it.

While denying they'd used the phrase in Parliament, National MPs used the phrase over and over again. There was a whiff of enjoyment about it. It seemed akin to warning someone that salacious rumours aren't true just for the opportunity to explain the rumours in detail.

The end point was that if you hadn't heard the phrase before, you heard it four times by the time one MP had finished denying being the source of the phrase. Not cool.

"Stupid little girl" is offensive and sexist. It draws attention to the Prime Minister's age and gender in a disparaging way, as if suggesting either quality may be the reason for any or all of her polarising decisions, faults or shortcomings. At the very least, it's rude. No party should tolerate the impression that one of their MPs said something so juvenile to the country's leader.

And it's embarrassing. It generated international headlines.

What is remarkable is how National cleverly turned itself into the victim. That's called political jujitsu. Flipping an awkward situation into a win for yourself.

Post-denial, National MPs quickly pointed the finger at the Speaker. It was his fault. He'd pushed the Stupid Little Girl story to the media. Then they ramped it up. They accused him of bias in the House. And then they acted up until he was forced to make that appear true.

On Wednesday, Paula Bennett delivered her meme line of the year. Nah, she teenaged. I'm "lay-ving". What a waste of time! And then she stormed out of the House.

Obviously not dramatic enough, things went up several notches the next day.

Thursday in the debating chamber was like watching a classroom of sugar-hyped nerds testing the patience of the teacher. Points of order, interjections, barnyard sounds and feigned ignorance led by the tag team of Bennett and Gerry Brownlee.

By the end of it, Mallard was forced to boot out Bennett. He looked as biased as the Nats claim he is.

Except he's not. Not in the debating chamber, at least.

Sure, Mallard is a heavy-handed Speaker who injects himself into proceedings far too much to allow the game to flow. He runs the risk of hypocrisy. It's hard to believe the man who once punched Tau Henare in the corridors of Parliament truly finds it offensive when an MP tells another to "settle petal".

But Mallard doesn't deserve to be accused of bias in the House. He's cracked down harder on the Government side of the House than the Nats, accused Labour MP Stuart Nash of acting like a naughty child and docked New Zealand First MP Shane Jones three supplementary questions just for laughing.

So, the villain here isn't the Speaker. The villain is the National Party, which at worst did say "stupid little girl", and at best thoroughly enjoyed exploiting the phrase. You choose. Either way, they lose.

Heather du Plessis-Allan is on NewstalkZB Wellington weekday mornings and is a columnist for the Herald on Sunday