A young teenage girl was forcibly stripped and kept naked in a police cell for almost an hour after being briefly forced into one of the spit-hoods banned in youth prisons ahead of the Northern Territory royal commission.

Key points: The girl was spit-hooded, stripped, and then kept naked in a padded cell for almost an hour

The girl was spit-hooded, stripped, and then kept naked in a padded cell for almost an hour Police said they denied her requests for a blanket to cover herself because of concerns about self-harm

Police said they denied her requests for a blanket to cover herself because of concerns about self-harm The NT ombudsman said police faced "urgent and extreme" circumstances, and cleared officers of wrongdoing

The girl's treatment was detailed in the annual report of the Northern Territory Ombudsman, who has backed the findings of an internal police investigation, clearing the officers involved of any breaches of duty.

Ombudsman Peter Shoyer said he was satisfied that police were acting out of concern about the "real and substantial" risk the girl would harm herself or the responding officers.

The girl had attempted self-harm in the back of the police van and kicked an officer who entered the vehicle's cage.

At the watch house she was stripped by five officers and kept naked in a padded cell for 50 minutes before she was given a blanket.

Mr Shoyer said he accepted that the removal of the girl's underwear and the length of time she was kept naked was not unreasonable in what police described as "urgent and extreme circumstances".

"There is an immediate, instinctive objection to keeping anyone naked for an extended period," he said.

"There would be few things in modern society that are more likely to eat away at the dignity and self-respect of an individual.

"However there are situations when police dealing with people who exhibit the most challenging behaviours have no alternative but to choose between limited and confronting options."

Despite the concerns about self-harm police failed to engage any mental health support as required by the girl's custody plan on file, which the ombudsman said would have been helpful.

He found that the use of the spit hood was not unreasonable and there was "no indication the complainant was upset or discomforted" by it.

The hoods were temporarily banned in youth detention centres after the Four Corners Don Dale expose and officially outlawed in 2017.

Unnecessary force 'inadvertently' used in restraint

The officer who was kicked in the police van was found to have then "inadvertently used a higher level of force than was required" in subsequently restraining the girl.

But the ombudsman said the officer did not appear to intend to cause the girl harm.

Excess force was 'inadvertently' used on the girl in the back of the police van. ( ABC News: Tristan Hooft )

At the watch house the decision to remove the girl's clothes and underwear was made partly on the basis of a previous incident in which the girl had used items of clothing including her underwear to attempt self-harm, the ombudsman said.

On that occasion the girl had struck out at officers who entered the watch house cell, injuring some including a female officer who suffered a broken cheek bone.

In the more recent incident the girl was spit-hooded while two female officers removed her underwear as three male officers pinned her down.

The girl had not spat at officers that day but was said to have spit and mucus on her face.

The ombudsman noted evidence that the forced removal of clothing can be especially traumatic for female prisoners, who are more likely to have experienced past sexual abuse or assault.

But he said the action was justified because "the complainant's behaviour in the past and on the day in question" meant the risk she might use clothing to attempt self-harm was real.

'Dynamic' situation with changing risk: ombudsman

That left the girl naked in a police watch house cell.

But the ombudsman also considered it reasonable for the officer in charge to twice deny the girl a blanket because of her "agitated response" when one was offered.

"It is important to appreciate that this was a dynamic situation where the assessment of risk was likely to change," the ombudsman wrote.

"With the resources that were available to the officer in charge, a review should not be too quick to substitute their own view for that of an experienced officer on the scene."

He said the officer was not confident the girl could not use a tear-resistant smock to attempt self-harm either.

The failure to contact the youth mental health support team despite the girl's distress and attempt at self-harm was an "important step" that was missed, the ombudsman said.

He also found that the video screens showing the inside of the girl's cell were visible at the reception desk and viewed by male officers and recommended greater privacy precautions.

Police jokes 'unhelpful' but not punitive

No findings were made against any of the officers involved in the girl's custody.

It was recommended police investigate alternative coverings to provide to people at risk of self-harm and review the girl's custody management plan.

The ombudsman said the case raised the need for police to review their training "for officers who are called on to respond in challenging circumstances like this case."

"These reviews should be conducted with particular attention to the needs and behaviours of young people and people who are experiencing mental health issues," he said.

The ombudsman also said that footage of the incident showed police expressing frustration, swearing and making "attempts at humour".

He did not provide detail but said comments needed to be seen "in light of the entire series of events."

"An isolated comment or action may always be drawn on to suggest that a particular decision was made to punish unruly behaviour or belittle a person in custody," he said.

"On balance, while some of the comments were unhelpful, I did not consider that was the case here."