The 21-year-old, who cannot be named, was found with about 2500 illegal images and is also accused of using his Nintendo DS to take explicit images of a girl, thought to be a relative.

His downloads were tracked by the Australian Federal Police, who began investigating in late March.

When they arrived, police say the man admitted downloading child pornography onto his laptop for the past three to four years.

The officers also looked at his Nintendo, finding images thought to be of his niece taken with the device in January 2010.

Police told the ACT Magistrates Court on Friday that they were still working through the images.

The defendant applied for bail before Magistrate Bernadette Boss on Friday morning, as emotional family members watched on.

The prosecution opposed his release, fearing he could interfere with witnesses and evidence, and may reoffend.

Dr Boss said she was particularly concerned about any intimidation of the man’s niece.

The man’s lawyer argued bail conditions could manage the risk, saying his client was now under the “very watchful eye” of the AFP and his family.

Electronic devices have been taken from the man, and his defence lawyer argued conditions could be put in place that he not use any such equipment.

Dr Boss refused bail, noting the prosecution case was strong, and that conditions could not manage the risk the man would intimidate or interfere with witnesses.

He will reappear in the ACT Children's Court – because he was a juvenile when the first alleged offence occurred – later this month.

Dr Boss noted he was a vulnerable prisoner and said he should only be in custody for as long as is absolutely necessary to protect the community.