Most parents and guardians rely on official age ratings when choosing films or computer games for their children.

A study by the Classification Office showed that 92 per cent of the respondents judged the classifications as important and 90 per cent valued the descriptive notes like 'contains violence'.

The numbers showed a substantial increase from the last survey in 2006.

The research was looking into the changing use of entertainment media and the public's knowledge and perceptions of the classification system.

According to the study, almost 70 per cent thought the classification system was "about right" and agreed with the work of the Government's censorship agency.

While the results were positive, new challenges continued to emerge, largely as a result of changes in technology and its role in shaping the use of entertainment media, the agency said.

The Office of Film and Literature Classification aimed to protect the public from harmful material.

It looked at films, literature, computer games, the internet and occasionally even videos recorded on mobile phones that contained text and or images dealing with sex, horror, crime, cruelty or violence.

- NZPA