The proposed watchdog's design is under the microscope of a parliamentary committee.
Independent MP and committee deputy chair Helen Haines raised concerns about the commission's reach.
The independent agency would investigate serious or systemic corrupt conduct across the commonwealth public sector and investigate ministers, politicians, their staff and officials.
Ms Haines questioned whether allegations of widespread Medicare rorts could be investigated, given the corruption of a specific public official wasn't involved.
Sarah Chidgey from the attorney-general's department said the watchdog's scope was designed to avoid the issue of external fraud against the commonwealth, as existing arrangements were in place.
Federal police have investigated 300 allegations of serious fraud in the past three years and the commonwealth prosecutors have received almost 1300 referrals from 30 agencies.
Shadow attorney-general Julian Leeser wants an external judge to decide whether hearings are made public.
He argues the commission could be guided by self-interest on public hearings to justify its $260 million budget.
Hearings would only be held in public under "exceptional circumstances", to be decided by the commissioner.
Mr Leeser said the threshold struck the right balance between holding officials accountable and protecting people's reputations.
The Australia Institute wants the exceptional circumstances test scrapped, saying it could undermine public confidence.
The think tank suggests the commissioner consider the risk of unfair prejudice to a person's reputation but not default to secret hearings.
Greens senator David Shoebridge also wants the commission to be more transparent and make its findings public.
Department officials said the commission was expected to publish its findings when it was in the public interest.
"If you expect it, why don't we say it? Why would you leave uncertainty?" Senator Shoebridge said.
The committee's report will be handed down on November 10.
Attorney-General Mark Dreyfus wants the legislation passed by Christmas to pave the way for the watchdog to operate by mid-2023.
The Human Rights Law Centre wants the government to work on wider whistleblower reforms before the anti-corruption commission comes into effect.
Senior lawyer Kieran Pender said the model was a good starting point but needed to go further.
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