The South Australian Labor party has pledged to introduce a state-based version of the Uluru statement, including establishing a representative body to act as a voice to parliament, if it wins the next election.

The proposal has been welcomed by Aboriginal leaders who say they are not prepared to abandon the resolutions of the 2017 First Nations National Constitutional Convention at Uluru despite a lack of support from the federal government.

Opposition leader Peter Malinauskas told Guardian Australia that the policy reaffirmed SA Labor’s support for negotiating with Aboriginal nations, a process that began in February 2017 but was halted when the Marshall Liberal government was elected just over a year later.

“Enacting a state-based version of the Uluru Statement from the Heart is an opportunity for Aboriginal South Australians to finally have their aspirations realised,” Malinauskas said.

The Uluru Statement from the Heart called for a constitutionally-enshrined Indigenous voice to federal parliament and the establishment of a Makarrata Commission to undertake a process of truth-telling about Australian history, and oversee a process of treaty-making.

Malinauskas made the announcement ahead of Naidoc week, which begins on Sunday and this year has the theme “Voice. Treaty. Truth.”

He said Labor would convene an Aboriginal working group to design the proposed voice to state parliament, with the model to be taken to the 2022 state election.

Elections for the First Peoples Assembly of Victoria, an elected body of 33-representatives that will negotiate the framework for the treaty with the Victorian government, will be held in September, with enrolment open now to all Victorian traditional owners, whether they live in the state or not, and to Aboriginal and Torres Strait Islander peoples who have lived in Victoria for at least five years.

The federal government oppose the Indigenous voice to parliament, which former prime minister Malcolm Turnbull dismissed as “undesirable” and a “third chamber of parliament”. Delegates from Uluru say that is not how they described or intended the proposal.

Federal Labor promised to hold a referendum on the Uluru statement, but lost the federal election in May.

SA opposition Aboriginal affairs spokesman Kyam Maher said that failure to implement the Uluru Statement would be unacceptable.

“It is evident the status quo is not working,” Maher said. “The gap between Aboriginal and non-Aboriginal people is widening in almost every tangible measurement.

“The time has come to stop telling Aboriginal South Australians, from the heights of the State Administration Centre, what is right for them.”

SA premier Steven Marshall, who has given himself responsibility for Aboriginal affairs and reconciliation, has continued negotiations with some Aboriginal nations around agreements for better service delivery but will not progress those agreements to treaties.

Narungga elder professor Peter Buckskin said he hoped Labor’s policy would receive bipartisan support.

“I would like to see all of the Uluru statement implemented,” Buckskin told Guardian Australia. “If we are ever going to achieve true reconciliation we have got to actually have a process for the truth telling in this state.”

Buckskin said his people were currently working toward an agreement with the Marshall government despite the formal halt to treaty talks, with Marshall himself visiting Narungga land to meet with elders.

“It’s not called a treaty like Labor would have called it but it’s still moving forward and building on a stronger, more responsive relationship with government in terms of delivering on agreed outcomes,” he said.

Adnyamathanha elder Vince Coulthard said his people were also in discussions with the Marshall government with a view to striking an agreement.

“But that’s all treaties are, an agreement between two or more parties,” he said.

He said Labor’s policy was “a great idea” but warned that First Nations people in South Australia would not accept lip service toward implementing the Uluru statement.

“If they are serious about it, it can happen and it can be a good thing,” he said.