Senior public servants have rejected claims the government has abandoned its initial design principles for a national anti-corruption commission.
Crossbench MPs, transparency advocates and lawyers are critical of the plan to hold hearings in private unless there are "exceptional circumstances" for them to be made open to the public.
That decision would be made by an independent commissioner giving consideration to the issue, any unfair risk to reputation or safety, and the benefits of public awareness.
Deputy secretary of the National Anti-Corruption Commission Group, Sarah Chidgey, said the request to include the "exceptional circumstances" test was made by the Attorney-General Mark Dreyfus, but did not say when.
"I wouldn't describe it as a deviation. We have added to those design principles a further requirement of exceptional circumstances," Ms Chidgey said.
Lawyers and transparency groups have told a parliamentary inquiry that the "exceptional circumstances" clause is vague, would severely restrict public hearings, and could lead to lengthy delays and legal challenges.
But Mr Dreyfus said the exceptional circumstances test ensures the commission strikes the right balance, noting only five per cent of New South Wales Independent Commission Against Corruption hearings are public.
The Accountability Roundtable — a group of senior former politicians and lawyers — said the inclusion was inconsistent with Labor's design principles outlined before the election.
"It is difficult to see what example would meet this test," the group said in a submission.
"Not only is the phrase ambiguous, it will provide an avenue for well-funded objects of an investigation to take court proceedings to stop a public hearing, but investigations will be long-delayed and made less effective in consequence."
Transparency International Australia said the exceptional circumstances clause was "simply unnecessary" given the proposed test was already stricter than most states with public hearings.
"It poses dangers for the effective operation of the commission — whether through tactical litigation or inaccurate political expectations or both," the group's chief executive said.
"This is due to its vagueness and uncertainty, as well as its underlying implication that specific but undefined extraordinary circumstances must exist to justify a public hearing."
NACC must cooperate with intelligence agencies to protect data
The department also provided an assurance that confidential and potentially classified information obtained by the NACC would remain secure.
Liberal senator James Paterson has raised concerns the NACC may become an espionage target if it holds classified information without appropriate safeguards.
Senior public servant Tara Inverarity told the committee the NACC must take reasonable steps to consult with intelligence agencies about how they "obtain, store, access, use and disclose" their information.
Arrangements may also be made for the classified information to remain on site, under the agency's control, but able to be accessed by NACC investigators.
Ms Inverarity also confirmed that subject to a warrant and a public interest test by a judge, the commission could raid a journalist's home as part of investigations.
Greens senator David Shoebridge asked whether investigators could require a journalist hand over a laptop or notebook with informant's details.
"If it is evidential material of a criminal offence then a search warrant authorises an executing officer to seize that material," Ms Inverarity said.
But that could only happen if a magistrate was satisfied "a very significant public interest test" had been met.
