These government Agency Sites can have useful information.

Advocacy
If your parent is having difficulty gaining services or support Advocates can often assist to advocate on your parents or your behalf.

Office of Public Advocates and Guardianship Boards
May have information on, and how to apply for,

• an Advocate to be appointed. or
• A Financial Administrator. This can be a responsible family member
• Or A Guardian. This can be a responsible family member

and info on making a,

• Power of Attorney
• Enduring Powers of Attorney (for some one to act on behalf of a person, at a time in the future, when the person is no longer unable to make their own decisions).
• Medical Powers of Attorney
• Guardianship
• Reviewing above Documents / Orders

For people with impaired decision making ability (with disabilities illness or mental illness). (Or for people likely to become impaired in the future).

Consult a solicitor, or Legal Aid Office for advice re above. Your local solicitor can advise you re making above declarations and documents.

The following are links to Office of Public Advocate and Guardianship Lists / Boards in Australia. Please Note Laws and Regulations vary in each state, and sites and information may change.

Victoria

Office of the Public Advocate - Victoria

Guardianship List - VCAT Victoria

New South Wales

Office of the Public Guardian

The Guardianship Tribunal

South Australia

Office of the Public Advocate (OPA) - South Australia

Western Australia Guardianship, Administration and Advocacy - Western Australia

Guardianship and Administration Board - Western Australia

Public Advocate - Western Australia

Northern Territory

Office of Adult Guardianship

Tasmania

Guardianship Board Tasmania

The Public Guardian

Some thoughts on above.
You may need to consider who in your family is the best person to take on responsibility for making financial or legal decisions or even decisions for instance regarding where a parent resides. (This person could already be performing this role. Having his/her role formalised or another to take on the role or specific tasks and have the role designated is important particularly when relating to statutory authorities and organisations).

Enduring Power of Attorney generally means that your parent can select in advance now (when legally competent to do so), the person they wish to take on and make decisions on their behalf for the inevitable time in the future when they are no longer able to make decisions for themself.

If a person parent has not got that capacity to make decisions, then it is often necessary to make application on their behalf, to the above authorities ( Guardian Boards) to make an order to appoint some one to act on behalf as a financial advocate or guardian. This needs to be a person who is recognised that they will act in the best interests of a person with mental illness or disability. Boards may appoint a variety of people. It may be a family member friend or government body or authorised organisation.

If you feel that some one is not acting in the best interests of the person with an illness or disability consult the above organisations and authorities. In most Australian States, Guardian Boards have authority to appoint new administrators or guardians where necessary or to review and revise arrangements.