Two members of a national advisory body have cast doubt on whether a referendum on recognising Indigenous people in the Australian constitution would be achievable by May 2017.

The date for the vote was backed by Recognise, the government-funded organisation charged with raising awareness of the issue, and Federal politicians.

But during a discussion panel at the Garrmalang Festival, a three-day Aboriginal and Torres Strait Islander cultural event in Darwin on Saturday, the Referendum Council's co-chair Pat Anderson AO said May 2017 was "not [an] achievable" date.

"It's not going to happen," she said.

Aboriginal and Torres Strait Islander Social Justice Commissioner Mick Gooda, who is also a member of the Referendum Council, said May 2017 could be achievable "if we get a wriggle on".

"But after July 2nd we will have a new Government," he added.

"At the moment the Prime Minister and the Opposition Leader are fairly committed to it, but one of them is not going to be there after the election."

Mr Gooda said the council was not working toward a deadline, and a "referendum moment" would emerge.

"Once we get that question right, the timing will take care of itself," he said.

May 2017 is significant because it would mark 50 years since the 1967 referendum which voted to count Aboriginal people in the nation's census for the first time.

Prime Minister Malcolm Turnbull and Opposition Leader Bill Shorten established the Referendum Council to lead the national conversation on recognising Indigenous Australians in the Constitution in December 2015.

All options still on table, forum hears

The growing debate on constitutional reform has also thrown up the question of a treaty — a position which was backed by IMPACT program coordinator Jade Jones-Cubillo.

"I think having a treaty is more powerful and more deadly for Aboriginal and Torres Strait Islander mob," she told the forum.

"You get self-determination [and] our sovereignty is recognised."

Ms Anderson and Mr Gooda said all options for reform were still being considered by the Referendum Council.

"I really love the concept of treaty, and I still reckon we can walk and chew gum at the same time," Mr Gooda said.

"We can still keep fighting for a treaty. I'm going to keep doing that, but I'm going to fight for constitutional recognition as well."

The next stage for the council is a series of leadership meetings, discussions with Aboriginal people plus a public education campaign.

"We are going to report to the Prime Minister and the Leader of the Opposition, whoever they may be now, before the end of the year," Ms Anderson said.

The crowd heard that if the referendum did not happen this time, it may have to wait another generation.

"Our very survival as the oldest living culture depends on you," Ms Anderson said.

Three-quarters support changing constitution

The latest forum in Darwin followed the release of Vote Compass data, which showed about three-quarters of Australians supported changing the constitution to recognise Indigenous people as Australia's first inhabitants.

Yet the data was at odds with the view of some Indigenous leaders, who did not support constitutional recognition on the ground it would only be symbolic, and not meaningful change for Aboriginal people.

There has also been concern the debate on constitutional reform has thus far not included a diverse range of Indigenous views.