Attorney-general Simon Corbell said the new merged agency would be required to give equal consideration to managing people's personal lives and their finances.

"Some concerns have been raised that bringing guardianship and financial management functions into the same office will result in a conflict of interest. The government does not agree with this view," he told the ACT Assembly when he introduced his Bill.

"Both guardians and trustees operate in similar circumstances and for similar purposes. They both make decisions for people with impaired decision-making ... Financial imperatives will not trump other considerations."

The Public Trustee's office manages finances for people who can't manage their own or when appointed by the courts. It is still dealing with the aftermath of a fraud uncovered last year, with two former staff and two contractors accused of stealing $1.65 million from clients.

The guardians act as a "manager of last resort" for people who can't make their own decisions, making medical, housing and other life decisions for people, and representing people with a disability at tribunal hearings on guardianship applications and represent forensic patients in tribunals and courts.

Although the merger won't happen until early next year, the government has already appointed the head of the Public Trustee's office, Andrew Taylor, as Public Advocate – putting him in charge of the guardians unit as well.

The move has outraged guardian staff and others in the sector.

A former head of the guardians unit, Heather McGregor, has described it as a "travesty" with potential for exploitation and abuse of Canberra's most vulnerable people.

The guardians unit says the merger shows a profound misunderstanding of the role of guardians, and the two offices should be "aggressively separated".

Human Rights and Discrimination commissioner Helen Watchirs has said the separation of the two offices ensured no single body was responsible for "the entirety of a vulnerable person's life".

But Mr Corbell said safeguards were built in.

A deputy Public Trustee and Guardian would be appointed and would be able to make decisions when the Public Trustee and Guardian identified a conflict of interest.

The function of acting as a guardian could also only be delegated to the deputy.

The safeguard recognised "the sensitive nature of a guardian or manager's role" and the high level of authority and responsibility the guardian had over a person's life. It also recognised the vulnerable position of the person under a guardianship or management order.

He also rejected fears that people would be charged fees for guardianship.

The idea came from Mr Taylor, who now heads both offices, and who told the government the merger would open up the possibility of charging. "There are many persons for whom management and guardianship services are provided that can afford and should pay for both services," he said.

But Mr Corbell said while the government did have the power to set fees for guardianship services, it had no plans to do so.

In another safeguard, the public advocate in the Human Rights Commission (a separate role to the guardians) would have the power to inspect the books and records of the Public Trustee and Guardian and other guardians and financial managers. The Disability and Community Services commissioner would handle complaints about the Public Trustee and Guardian.

Mr Corbell conceded that approaches to dealing with the clients differed between the trustees and the guardians, but said the new single office would be more accessible and "bring a wider perspective and range of skills and experience to the protection of the best interests of clients".

The government is also restructuring the Human Rights Commission and other commissioners into a single agency.