A Palmerston man who installed a hidden video camera in his stepdaughters' bathroom for "salacious and sleazy reasons" has walked from court with a suspended sentence.

The father, who cannot be identified for legal reasons, pleaded guilty to installing a motion-activated camera disguised as a clothes hook in the bathroom of the Durack house he shared with his partner and her two daughters.

His now ex-partner, who he was with for nine years, discovered the camera after it fell off when she tried to hang her dressing gown on it.

The offender said he installed the camera because he was worried about his stepdaughters self-harming, but Judge Greg Cavanagh rejected that explanation, saying he did it for "salacious and sleazy reasons not to do with concern for the safety of the girls".

"I find your explanation that you did this for benign, or to use your words - 'pure reasons' - fanciful, not worthy of belief and incredible. I do not accept them," Mr Cavanagh said.

The man, who represented himself in court, said he became increasingly worried about the behaviour of his two stepdaughters and believed they were at risk of self-harming.

"I decided the best place to monitor self-harming behaviour was in the area in question," he told the court.

He said he did not raise his concerns with the girls' mother because of concern for her wellbeing.

'What's wrong with you?': Man confronted by girls' mother

Prosecutor Richard Burton read out extracts of the mother's statement to police detailing the man's reaction when she confronted him about the camera.

"He started crying and saying he bought [the camera] when he was drunk and never intended to use it," the statement said.

"What is wrong with you?" asked the mother, to which to the guilty man replied: "I was curious".

"Curious about what?"

"I don't know," he said, according to the mother's statement.

She urged him to report himself to police and then ended the relationship, the offender told the court.

In sentencing the man, Judge Cavanagh said there was no suggestion that any other action was taken besides putting the camera in the bathroom.

"But such conduct from a person like you, in a position of trust ... must be deterred," he said.

The offender walked from the court with a suspended four-month jail term and could be sent to prison if he commits another offence within three years.