A Tasmanian court has heard children as young as five were depicted in sexual acts on a man's computer which contained 2 million child exploitation images.

Ross Andrew Cooper, of West Hobart, has pleaded guilty to accessing and downloading the images from the internet since 2001.

The 47-year-old told the court he had become "addicted" to the images while trying to test how easy it would be for his children to access them on the internet.

The court heard he viewed and downloaded the images daily and had paid almost $10,000 over eight years to access the material.

He catalogued them on a hard drive, thumb drive and disks.

The crown prosecutor told the court Cooper was worse than those who sought out free material because his paid membership of at least 100 sites maintained a commercial demand for the exploitation of children.

Cooper will be sentenced on May 17.