Mystery continues to surround an alleged slur against the Prime Minister.

The comment was thought to have been made during Question Time earlier this month when a National MP sitting near leader Simon Bridges reportedly called Jacinda Ardern a stupid little girl.

Bridges has investigated but says there's no proof it was ever uttered.

"I didn't say it, I didn't hear it. I was close to the people who supposedly did. Was it even said."

He says while he's not excusing it, calling politicians names is all part of the cut and thrust of parliament.

"The speaker, I don't mean no criticism of him because he backtracked and apologised, he called Stuart Nash a silly child. I think the day after we had Winston Peters call Nathan Guy a fool."

Jacinda Ardern herself says she was unable to say who was responsible for the insult.

"I heard a lot of noise from across the side of the house. It was quite hard for me to pick out one single comment.

Asked how she felt about being called that, she says: "Look, plenty of this stuff flies around the house, but as I've always said, I'd rather play the ball, not the man."

More accusations around sexist comments were made in Parliament time.

Defence Minister Ron Mark was answering a question from National's Maggie Barry.

He replied to her interjection telling her to 'settle petal'.

Speaker Trevor Mallard told him to withdraw and apologise - saying that sort of sexist remark is unacceptable.