Children with mental illness, prisoners and prison guards are being forced to mix in Royal Darwin Hospital's secure mental health facility — sparking calls for urgent action before "someone is harmed".

Key points: Anti-discrimination commissioner Sally Sievers says the Joan Ridley Unit has never been "fit for purpose"

Anti-discrimination commissioner Sally Sievers says the Joan Ridley Unit has never been "fit for purpose" Ms Sievers says she's been raising concerns about the facility with NT Health since 2016

Ms Sievers says she's been raising concerns about the facility with NT Health since 2016 NT Health says the unit "is one part of a much broader system that NT Health is continuously working to strengthen"

Anti-discrimination commissioner Sally Sievers said the issue of patients mixing together in the Joan Ridley Unit, designed for people with acute psychiatric problems, was a longstanding problem.

However, Ms Sievers said in the last year the number of prisoners housed in the secure ward appeared to have increased, triggering fresh safety concerns.

"From my point of view, there's no doubt that prisoners are absolutely entitled to mental health care, but when they come, they come with two prison guards as well," she said.

"You get a very small space with a really diverse mix of people."

Ms Sievers is calling on the NT Government for urgent action so prisoners, guards, men, women and children no longer had to share the same space.

"Something is going to happen to someone on that ward — someone is going to be harmed," she said.

"This is the number one priority in mental health."

Joan Ridley Unit is at Royal Darwin Hospital in Tiwi. ( Supplied: Jack Bullen )

Not 'fit for purpose'

Ms Sievers said the Joan Ridley Unit had never been "fit for purpose", and the design was unsuitable for the mix of people housed there.

The anti-discrimination commissioner said she had been raising concerns about the facility to NT Health since 2016, with very little change.

She has outlined her concerns in the Community Visitor Program's Annual Report 2018-19, tabled in NT Parliament this week.

"The time for talking and tossing around options is over — there needs to be change in the actual unit," Ms Sievers said.

The long-term solution was a new unit, she said, and urged the NT Government to increase its spending in mental health to help care for vulnerable Territorians.

"Across the whole of Australia, there isn't enough money being put into mental health," she said.

AMA NT and Ms Sievers want more funding in mental health to help vulnerable Territorians. ( Supplied: Vetta )

"It is concerning that the Northern Territory public mental health services funding is one of the lowest per capita in Australia."

Australian Medical Association NT president Dr Rob Parker was also concerned about the facility and echoed calls for more funding in mental health.

"It's simply not fit for purpose any more — it needs to be replaced," he said.

"And there's just not enough money in mental health."

A 'sustained requirement for mental health inpatient beds'

In a statement, a spokeswoman said NT Health welcomed the NT Community Visitor Program's annual report.

"Department of Health acknowledges the need to grow capacity and deliver separation of service in a safe and sustainable way and we are continuing to work through options to achieve this," she said.

"The NT has unique challenges, having a small population with relatively high mental health needs."

The spokeswoman the Joan Ridley Unit was "one part of a much broader system" which NT Health was continuously working to strengthen.

The Health chief executive officer has also offered to meet with Ms Sievers to discuss issues with the unit and provide input into this work.