Scott Ian Whittaker, 38, pleaded guilty in the ACT Magistrates Court on Monday to 22 new charges, including seven counts of engaging in sexual intercourse with a child in 2018.

The other charges included multiple counts of using the same teenager for the production of child exploitation material, and committing acts of indecency on the underage girl.

Whittaker had spent the past fortnight waiting to learn the outcome of a comprehensive police investigation, with prosecutors having foreshadowed that the new charges were likely to be forthcoming.

He had previously pleaded guilty to three offences involving the possession or control of child abuse and exploitation material, and the improper storage of firearms.

Police said earlier this year that the initial charges had been laid after searches in Fyshwick and Bonner uncovered two guns, as well as a phone and laptop that contained objectionable videos and pictures.

The precise facts of Whittaker's offending are yet to be aired in court.

The 38-year-old's latest pleas on Monday morning prompted a brief confrontation with another defendant in the courtroom corridor.

As Whittaker left, a man on his way to the bar table to answer charges of his own angrily whispered at him.

This did not impress Magistrate Peter Morrison, who reprimanded the man and told him his commentary was "not on".

Outside court, the man told The Canberra Times he had called Whittaker a "disgusting dog" after listening to the 38-year-old's lengthy list of horrendous crimes.

Whittaker is likely to be committed to the ACT Supreme Court for sentence when he fronts the Magistrates Court again next Monday.

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