The Office of Film and Literature Classification has released a study of the 200 most-watched online porn videos.
Mr Shanks said the analysis of the huge online porn site Pornhub found that 46 percent of the most viewed videos featured a narrative of sex between step-siblings or parents.
In many of these videos, initial refusals of sexual activity would be overcome by pressure or persistence by a partner.
He said 35 percent of the clips had some non-consensual behaviour in them, although New Zealanders generally preferred content not classified as extreme.
Mr Shanks said the research would help understanding about what people were viewing and would inform education programmes for young people.
"It is clear from this latest work that porn provides a very poor model for young people who are developing their understanding of consent and what a healthy sexual relationship looks like," he said.
New Zealand had an opportunity, he said, to be an international leader in getting other countries to join together to force online porn sites to do more to make it harder for young people to access porn.
He supported in-principle work in the UK to make people sign up and provide age verification to access porn sites, he said.
The report said the step-porn trend was popular in many countries, but none of the videos depicted sex between real family members - instead using the taboo of the sex as an erotic fantasy.
The stories tended to be highly contrived and unrealistic.
He said mainstream porn was often considered aggressive but the research team was surprised to find that it was a feature in only 10 percent of the popular videos, and that viewers tended to prefer consensual behaviour.
The report said New Zealanders were the 13th most frequent visitors to Pornhub per capita.
Professionally recorded porn was more than twice as popular as homemade porn. The categories most common among the popular videos were "high-definition" porn, followed by "popular with women", then "pornstar", "teen" and "babe".
Only one of the videos showed 'choking', though 13 percent showed 'throat holding'. Only 3 percent showed condom use.
