Whenever an MP says something deemed to be 'unparliamentary' in the House, they are asked to withdraw and apologise - but it doesn't happen often.
This year there have been a number of unparliamentary incidents - most recently when National MP Nicky Wagner called Labour MP Deborah Russell a "bitch".
MPs are banned from unbecoming language, insults, and accusations of dishonesty, and what is considered to be 'unparliamentary language' varies over time.
Parliament records show that in 1949, "humbugs" was considered unparliamentary, in 1963 frowned-upon language included the phrase "energy of a tired snail returning home from a funeral" and in 1977 someone was told off for saying "sober up".
There have been plenty of sexist remarks thrown around the House in the last few months, but it is relatively rare for an MP to swear in Parliament.
When they do swear, it often causes tension in the House - even if they are quoting another person.
Here are some notable examples:
August 2008: Sue Bradford quoting a case worker who said "f**k off"
Former Green MP Sue Bradford recounted an anecdote from a beneficiary who was told by a case worker to "f**k off".
She was told to withdraw and apologise for repeating the statement in Parliament.
November 2004: Lianne Dalziel said the words "sl*t" and "wh*re"
During a debate, Labour MP Lianne Dalziel said the words "sl*t and wh*re" in relation to a hypothetical situation, which National MP Judith Collins took exception to.
However she was not required to withdraw and apologise, and the debate continued.
March 2003: Marc Alexander said "wh*re"
"That is nothing more than political correctness dressed up in a wh*re's skirt," said United Future MP Marc Alexander.
It appears he was allowed to continue speaking after the remark.
May 2015: Ron Mark said the phrase "shut the f*** up"
NZ First MP Ron Mark reportedly said "shut the f*** up" while in opposition in May 2015.
It came during a debate between Bill English and Grant Robertson, Stuff reported.
He withdrew and apologised for the remark.
May 2007: Lockwood Smith said "poor p***k"
"I laugh because I feel sorry for the poor p***k," said National MP Lockwood Smith during a debate on taxation.
The debate continued after his comment.
August 2006: Ron Mark pulls the finger three times
Technically not a swear word, but it has a similar effect.
NZ First MP Ron Mark pulled the finger three times at National MP Tau Henare in Parliament.
He apologised for the gesture.
Bonus - August 2017: David Seymour calls MP "f**king idiot"
It wasn't in Parliament, but ACT leader David Seymour called NZ First MP Richard Prosser a "f**king idiot" during a speech at a pre-election business conference last year.
It came after Mr Prosser had urged those with shares in Contact Energy to sell them immediately.
"Well, I realise in a role such as mine you are supposed to have a certain amount of decorum," he said.
"But that makes me really angry - what a f**king idiot."