People with disabilities are at "serious risk" of being sexually and physically abused in Australian prisons, and are disproportionately held in solitary confinement, according to a new report by Human Rights Watch (HRW).

The damning investigation, published on Tuesday, examined 14 government and private prisons in the states of Queensland and Western Australia, detailing experiences of sexual and physical abuse, as well as the treatment of prisoners with disabilities.

The report found instances of prisoners living in nappies (diapers) due to lack of adequate toilets.

"It confounds me that in modern Australia a prisoner with a physical disability would have to wear a nappy simply because there is only one suitable toilet - and it is located in an infirmary," Elaine Pearson, Australia's head of Human Rights Watch, said.

The report also found high levels of solitary confinement among those living with disabilities.

Prisoners with pyschosocial or cognitive disabilities were found to be disproportionately placed in solitary confinement, at times for up to 22 hours a day. This had a "devastating" effect on the prisoners, HRW said.

One man with a cognitive disability was found to have been in solitary confinement for 19 years, the report found.

When approached for data, the state of Western Australia said it did not record specific data on the numbers of prisoners with mental health disabilities being sent to solitary confinement.

The HRW investigation is based on interviews with 275 people, including 136 current or recently released prisoners with disabilities. HRW documented 32 cases of sexual violence, allegedly perpetrated by other prisoners and staff. It also documented 41 cases of physical violence.

"They are perceived as weak by other prisoners and are routinely bullied and harassed, particularly for their medication," lead researcher Kriti Sharma told Al Jazeera.

Pearson called on Australia's states to better train prison staff in recognising cognitive disabilities, and to hold independent inquiries into the use of solitary confinement.

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She also called for the independent inspection of facilities.

While Western Australia had an independent inspector, that was the exception, rather than the rule, she said.

The report said reforms were needed regarding how prisoners were screened to detect disabilities when first entering prisons.

Lack of communication, especially between Aboriginal prisoners and prison staff, was identified as a key issue. A 2010 study found that up to 94 percent of indigenous inmates in Northern Territory jails experienced some form of hearing loss, but was frequently unaccounted for.

Aboriginal prisoners especially affected

While fewer than three percent of Australians are Aboriginal, official data shows that indigenous people make up more than a quarter of the prison population.

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Aboriginal people who are sent to prison are more likely to be living with a cognitive disability, according to Damian Griffits of the First Peoples Disability Network.

"Aboriginal and Torres Strait Islander people experience disabilities at a much higher rate than the rest of the population," Griffits told Al Jazeera.

"If you're an Aboriginal person in parts of remote Australia with pyschosocial disabilities you're more likely to end up in the back of a paddy wagon (police truck) than to receive help for your disabilities," he added.

The report comes on the back of a Royal Commission into the detention of youth in Australia's Northern Territory last year.

That inquiry was prompted by the release of shocking footage that showed mostly Aboriginal teenagers being tear gassed while confined in prison, as well as being held in sensory deprivation "spit hoods".

HRW's Pearson singled out the states of Western Australia and Queensland for being "open enough" to allow access to prisons for the report's research.

In a statement, the Queensland government said it was implementing the recommended reforms found in a parole review report and developing a 10-year plan, which would encompass issues of disabilities among prisoners.

Western Australia said staff receive training in handling prisoners with mental health issues, including in-person training on working with people with disabilities in prisons, as well as online modules.