The video also appeared on Twitter.
Justice Minister Andrew Little has indicated it is time for a review of the country's hate speech laws and has said he would fast-track a review of the Human Rights Act, which could see a crackdown on hate speech.
He said the current hate speech laws were not strong enough and said they needed to change.
Speaking to Q&A, Clark agreed with Little and said it was "time to have a look at the law in light of what is happening in society".
Her report said the current laws governing hate speech on social media was a "patchwork of legislation much of which pre-dates social media".
She said the current law only deals with hate speech on the grounds of creating racial disharmony, or disorder.
She said the law needs to be expanded to account for hate speech against people in the Rainbow community, for example.
The attack in Christchurch, Clark said, was carried out by a violent extremist who communicated with his peers in closed groups on social media platforms.
"What I am concerned about is that the rising level of rhetoric on social media, from people who think they can get away with just about anything – and let's face it, they can."
She said she has regularly reported hateful content online and often her reports were dismissed.
The New Zealand Media Council and the Broadcasting Standards regulate media content – Clark said a similar body is needed for social media.
Meanwhile, Clark said Ardern has a real opportunity to create change at the Christchurch Call this week.
"New Zealand is in a leadership role. What she is proposing with others with the Christchurch Call is around terrorist and violent extremism."
