Commentators who joined in a vicious online attack against a new Christchurch principal will be prosecuted, police say.

Burnside High School principal Warwick Maguire has spoken to police and those who posted defamatory comments on social networking site Facebook would face criminal charges and civil investigation, Papanui senior sergeant Pete Stills confirmed to the Wanganui Chronicle.

Mr Maguire, who moved from Wanganui High School to became principal of Burnside High last November, has been targeted by a Facebook group called "I Hate Burnside's New Principal!!!".

The site attracted more than 300 members who made defamatory, offensive comments about Mr Maguire, and criticised changes he has made to the school, before it was brought to police attention and shut down.

A second page dedicated to the first page was put up and attracted about 150 members before it was also taken down.

Mr Maguire was away on leave when the pages were active but he spoke to police on his return.

"It has not been amusing for Mr Maguire or his family, who have been hurt by the comments," Mr Stills said.

"Some of the comments are clear criminal offences. They are clear threats made toward Mr Maguire that cannot be ignored."

Meanwhile, a Facebook page put up in support of Mr Maguire called "Warwick Maguire is a great principal and a good man", has drawn more than 800 members.