Australians are poised to vote in a historic referendum which could see it change its constitution for the first time in almost 50 years.

If approved, the vote on 14 October would establish an Aboriginal and Torres Strait Islander Voice - a formal body for Indigenous people to give advice on laws.

PM Anthony Albanese argues it would be a "simple" change to improve the lives of Indigenous Australians.

But constitutional referendums in Australia are rare and difficult to pass - only eight of 44 have succeeded.

And the Voice proposal is the subject of fierce debate - with both support and opposition across the political spectrum.

What is the Voice to parliament?

The Voice was recommended by a historic document in 2017 called the Uluru Statement from the Heart.

Drafted by more than 250 Indigenous leaders, the statement is considered the best - though not unanimous - call to action for reforms which affect First Nations Australians.

When announcing his plan to hold a referendum in March, Mr Albanese said the Voice would enshrine "recognition" that Australians "share this great island continent with the world's oldest continuous culture".

"Our nation's birth certificate should recognise this and be proud of it," he added.

The proposal states the Voice will "make representations" to MPs and policy makers "on matters relating to Aboriginal and Torres Strait Islander peoples".

However, if the referendum passes, parliament would have the power to decide on the Voice's composition, functions, powers and procedures.

What's the case for it?

Indigenous Australians feel a "powerlessness" when tackling structural problems to improve their lives, the Uluru Statement says.

These problems include having a shorter life expectancy than non-Indigenous Australians, disproportionately poorer health and education outcomes, and higher incarceration rates.

Many argue this is often because of a failure to properly consult Indigenous people on solutions.

"Non-Indigenous people [are] making decisions about communities they have never visited and people they do not know," wrote Prof Megan Davis, an Uluru Statement signatory.

What do opponents say?

Some argue Indigenous people are already represented fairly in parliament. It currently has 11 Indigenous lawmakers - representing 4.8% of the parliament, a slightly higher percentage than the Indigenous Australian population nationwide.

But Voice supporters counter that MPs represent specific constituencies, not necessarily Indigenous interests.

Other critics say it could act like a third chamber of parliament and potentially veto legislation, but the government has ruled this out.

Support is not universal among Indigenous people, either. Some say a treaty with Indigenous people - a legally binding, negotiated agreement - should be the priority. Australia is the only ex-British colony without one.

Many Indigenous Australians emphasise they never ceded their sovereignty or land. There are fears that being recognised in the constitution could amount to that.

And others argue it's just a symbolic gesture and that money could be better spent on immediate solutions.

What will the Voice look like in practice?

That's not yet certain. If Australia votes yes, legislation designing the Voice will then be developed and debated.

One proposal suggests the advisory body could have 24 members - comprised of representatives from each state and territory, the Torres Strait Islands, and remote Aboriginal communities.

Mr Albanese sees the Voice being "an unflinching source of advice and accountability".

Are there global comparisons?

Voice advocates compare it to the First Nations parliaments in Norway, Sweden and Finland for the Sami people.

They're not parliaments in the traditional sense - they are mostly consultative bodies which do not have a formal legislative function.

In Finland, for example, the government negotiates with the Sami Parliament on specific matters like land management and legislative or administrative changes affecting Sami culture.

However, Finnish laws don't prevent government authorities from forging ahead without negotiations.

Why is a referendum needed?

Advocates say the Voice needs to be enshrined in the constitution rather than legislated. Such a change cannot happen without a referendum.

They argue this would give the Voice permanency, insulating it from partisan politics.

For it to succeed, a majority of Australians need to vote yes. There also needs to be majority support in at least four of Australia's six states.

Polling has previously indicated about three quarters of Australians support a constitutionally enshrined Voice - but that has been dropping since the debate began in earnest.

The result is far from assured - the last successful referendum was in 1977, and none have passed without bipartisan support.

In this vote, Australia's main opposition coalition is campaigning against the change.

The Greens party will support the Voice. But its previous Indigenous Affairs spokesperson, Lidia Thorpe, recently left the party over its position - she is advocating for a treaty first.

What next?

Australians will head to the polls on 14 October, where they'll be asked to write 'yes' or 'no' on their referendum ballots. Results are expected to begin flowing in that evening.

If the vote is successful, the parliament will turn to discussing how to build the body, and the government will look at the next steps outlined in the Uluru Statement.

It also calls for a Makarrata commission - a body to supervise a process of treaty-making and truth-telling about the history of Indigenous Australians.

Implementing a Voice is also seen as likely to create further impetus for an Australian republic. Mr Albanese has already indicated a referendum on the issue is likely if he wins a second term in 2025.

His government has refused to be drawn on what will happen if the proposal fails - for example, if it will try to create a body without enshrining it in the constitution.

Additional reporting by Tom Housden