The 16 members of the Greens are embarking on a two-day retreat in Victoria, before federal parliament returns, to thrash out their internal differences over the Indigenous Voice to Parliament.

The Greens' First Nations spokesperson Lidia Thorpe wants a Treaty first and has dismissed the Voice as a powerless advisory body which she is threatening to oppose unless she is satisfied that "First Nations sovereignty is not ceded".

Her stance is at odds with many of her Greens colleagues who are in favour of enshrining the Voice in the constitution, and are both frustrated that the internal debate has yet to be settled, and uncomfortable with the prospect of adopting a divided position.

One Greens member pointed to the Resolve Political Monitor, published in the Sydney Morning Herald, which found 87 per cent of Greens voters surveyed supported the referendum.

As the grassroots campaigns for the Yes and No sides take shape, and Australians ready themselves to vote in the country's first referendum in 24 years, insiders predict the Greens will ultimately endorse the Voice and allow Senator Thorpe to break ranks and vote no.

While technically allowed under the Green's constitution, such a position would confirm a rare split in the party which has become a powerful voting bloc in the 47th Parliament of Australia, providing stability for the Albanese government to enact its agenda.

Without Senator Thorpe's vote, Labor would need to rely on the support of other crossbenchers in the Senate to pass legislation firstly to establish the referendum and then to create the Voice, if that referendum succeeds.

The federal government is firmly of the view that inserting an Indigenous Voice into the constitution would not have any impact on sovereignty, with the assistant Minister for Indigenous Australians Malarndirri McCarthy labelling Senator Thorpe's argument a "misnomer".

"I'm a Yanyuwa Garrwa woman from the Gulf of Carpentaria. We've never ceded. Do you think I would stand by and let that happen?," Senator McCarthy told ABC's Q+A program.

"So, please, it is a misnomer. Sovereignty will not be taken over or lost in this process."

Senator Thorpe, who was also on the Q+A panel, said she wanted that assurance written in legislation or in the constitution, a demand the government is almost certain to reject.

Sovereignty means legal control over a territory, including the ability to make laws that apply to the people of that territory and enforce them.

From a legal sense, that kind of sovereignty "has long been lost by Aboriginal and Torres Strait Islander peoples", according to University of Sydney Professor of Constitutional Law Anne Twomey.

"The High Court has recognised that Aboriginal people and Torres Strait Islanders are subject to Commonwealth, State and Territory laws, along with everyone else in Australia," she said.

"If sovereignty is taken in its legal sense, then that sovereignty is now held by the Crown, as recognised both in the Mabo case and the Uluru statement."

Professor Twomey said the problem with the term 'sovereignty' was that it is used to mean different things, and can be as much a spiritual or political notion, to some, as it is a legal one.

This is reflected in the Uluru Statement From the Heart which says "our Aboriginal and Torres Strait Islander tribes were the first sovereign Nations of the Australian continent and its adjacent islands" but goes on to describe this sovereignty as "a spiritual notion".

"It has never been ceded or extinguished, and co-exists with the sovereignty of the Crown," the statement asserts.

Prime Minister Anthony Albanese has repeatedly challenged both the Greens and the Coalition to support the referendum which is due to be held in the second half of this year.

"It's about respect," Mr Albanese said.

"The vote that will occur later this year will be about just two things: it will be about recognition and it will be about consultation on matters that directly affect Aboriginal and Torres Strait Islander peoples."

Opposition Leader Peter Dutton — who has been demanding more detail from the government — is set to attend this week's referendum working group meeting for a briefing on the Voice, as the Liberal Party grapples with its own position.