A Christchurch man has been sentenced to two years and one month in prison for the possession of almost 30,000 child sex abuse images and videos.

Corey Andrew Challis pleaded guilty to two charges in May.

The 34-year-old stored the material on his work computer and external hard drive.

Challis was convicted of a similar offence in 2009, where he was sentenced to community work and supervision.

Department of Internal Affairs Censorship Manager Stephen Waugh says it is of particular concern when offenders download and view child sexual exploitation while at work.

He says they are focused on eliminating the abuse the creation of this material subjects children to as well as the effect of the material on homes and the community.