The federal opposition says Indigenous Australians Minister Linda Burney needs to clarify whether the date of Australia Day is an issue the voice could advise on.
Facing opposition questions in parliament on Tuesday, Ms Burney said the voice - which will be put to a referendum later in the year - would not advise on "parking tickets ... changing Australia Day (or) all of the ridiculous things that that side has come up with".
A key figure in the design of the voice, Tom Calma, told The Australian advice on shifting Australia Day could be put to the government if it was seen as a priority for the body.
But he said there would be many other priorities for the voice in terms of improving Indigenous wellbeing, well ahead of anything to do with Australia Day.
Liberal deputy leader Sussan Ley said the government was not being genuine in answering questions about the parameters of the Indigenous voice.
"It is simply not good enough for Linda Burney to say in the parliament the voice will not make representations on Australia Day and she ruled out other matters that we questioned her on as well," Ms Ley told reporters in Canberra on Wednesday.
"She's now being contradicted by experts, including those on the 'yes' campaign and her own referendum working group - they've taken a completely different position."
Ms Ley said voters wanted answers from the government ahead of the referendum, which is due to be held between October and December.
"We're not asking them for the same political motives that I detect in the government - we're asking them on behalf of the Australian people."
Independent senator Lidia Thorpe, a proponent of the 'no' case, said the voice should have the power to advise on any topic if the referendum was successful.
"There should be no limits," she told AAP.
"What the minister has come out with is clearly an indication of how powerless this voice really is.
"They're already coming out and undermining this person or the group of people on what they can and can't do."
Prime Minister Anthony Albanese told the Ten Network on Tuesday he expected the voice to offer advice on "practical issues of education, health, housing (and) incarceration rates".
