The anti-corruption commissioner’s former executive assistant has been fined $5000 for breaching the ICAC Act after disclosing confidential information on Snapchat.

Kate Taylah Johnson, 23, pleaded guilty in Darwin Local Court on Monday to breaching Section 145 of the Act, relating to disclosing information obtained in the course of her work.

However, a Criminal Code charge of disclosing confidential information was withdrawn.

The court heard Johnson photographed part of a handwritten letter from an inmate at the Holtze prison to Commissioner Michael Riches on May 31 and posted it to social media site Snapchat, where it was viewed by more than 100 people before being deleted.

The letter is understood to have related to a seemingly frivolous complaint by the inmate.

Police questioned Johnson about the leak of information on June 3, when they also found a video on her phone related to the breach.

“It’s a serious breach of trust … it’s crucial that members of the public have faith that confidential communication with all government agencies will be sacrosanct,” prosecutors said.

“The defendant’s actions have undermined the confidence that the public has in ICAC and the public service in general.

“The sentence must serve as a reminder to public servants and to people in a position of power that they cannot abuse their position for any reasons.”

Judge David Woodroffe considered 29 character references for Johnson in determining the sentence, as well as assurances from her lawyer Julie Franz that Johnson had felt “deep regret” about the breach and that her actions had caused her “personal loss”.

Her lawyer said she resigned from her job as Mr Riches’ executive assistant – which saw her function as the secretariat of the ICAC’s Operations Committee which received reports from investigators and provided recommendations to the Commissioner – after the breach.

Johnson was fined $5000, plus a $150 levy, with no conviction recorded.