A principal in New Zealand has caused a national storm after he was caught hoarding porn on his school's computer for more than 15 months.

While Northcote Intermediate principal Michael Wilks's school network was protected by filtering software, his machine was not because of his status.

The 66-year-old was dismissed by his board of trustees after an examination of pornographic material found on his computer during maintenance.

Police and the board of trustees have refused to specify the nature of the material he had been accessing, but it is understood to have included child pornography.

There has been an outcry as to why he has not faced criminal charges. More than eight other New Zealand teachers have been sacked for accessing pornography on work computers in the past year but none has been charged.

Auckland police say the material has been passed to Internal Affairs for assessment.

According to the New Zealand Herald, Northcote teachers went from class to class explaining what had happened from a briefing sheet which said: "Remember at the beginning of the year and your parents had to sign a contract before you were allowed to use the internet at school? Well, this standard did not just apply to you, we expected everyone at our school to be obedient to this."

It went on: "Unfortunately we had some really bad news during the holidays. When the computers were being updated it was found that Mr Wilks had been misusing his computer."

Interim council director Harvey McQueen confirmed that in the past 11 months eight secondary and primary teachers had been deregistered, or were in the process of being deregistered, after being sacked for accessing pornography at school. None of the cases involved criminal charges.