Anita Phillips, in her 2012-13 annual report, says mental health patients and prisoners at Canberra's jail have gone without representation because the territory's one mental health advocate cannot handle the case load.

The report shows a 5 per cent increase in the number of clients brought to the public advocate in 2012-13, but a drop in the number of patients given assistance to protect their human rights.

In the report, Ms Phillips said the situation had forced her office to reduce the amount of prisoners with mental illnesses it assisted at the Alexander Maconochie Centre, as well as cutting the amount of advocacy per prisoner by 50 per cent.

The cuts come as separate figures, contained in the Justice and Community Safety directorate's annual report, show a large number of inmates are being held in the 10-bed Crisis Support Unit for an average of almost a month.

The unit, designed to deal with short-term mental health crises, held 59 inmates for longer than two weeks at a time in 2012-13.

Each detainee was held for an average of 29 days, although that average may be skewed by inmates staying in the unit on a near-permanent basis.

Ms Phillips predicted problems for her office in her 2011-12 report and said the situation had played out ''as pre-empted'' with the demand for advocacy in 2012-13 exceeding ''the resourcing of a single staff member''.

Her report warns it is ''beyond the capacity'' of the public advocate to meet demand and ''inevitably this will result in a re-evaluation and rationalisation of whom the PA ACT can support''.

On Tuesday, Ms Phillips said she her office needed funding for at least one more mental health advocate.

But the government, with a budget under pressure, said savings would have to be found elsewhere to pay for extra front-line workers.

Attorney-General Simon Corbell is considering a restructure of the territory's rights protection agencies, including the public advocate and the Human Rights Commission, and also potentially the Victims of Crime Commission and elements of the Public Trustee.

Mr Corbell said he was in talks with the territory's statutory office holders but one option was to centralise the administrative and back-of-house components of the agencies to free up funds for essential services.

''I haven't explicitly said they should be merged,'' he said.

''We need to look at ways to reduce duplication.

''I do have a view that we could be using our rights protection dollars more effectively.''

Ms Phillips said understaffing meant some patients and prisoners were ''falling through the net''. Her report shows that her office received 4591 notifications about 1029 adults in the mental health system in 2012-13, up from 4500 the previous year.

It shows 364 were provided with advocacy, down from 394 the previous year.

Ms Phillips predicted that advocacy would continue to decrease as demand and the complexity of cases grew, particularly in areas such as adolescent mental health.