Voters won't know the date of the Indigenous voice referendum until about a month out from the poll.
The formal 'yes' and 'no' cases for the constitutional change will be published online on Tuesday by the Australian Electoral Commission, ahead of a pamphlet mailout and a vote between October and December.
But Prime Minister Anthony Albanese flagged on Monday he would leave the announcement of the referendum date until at least September.
It was thought Mr Albanese would announce the date when he attended the Garma Festival in the Northern Territory in early August.
"I don't plan to announce the date at Garma because that's just in a couple of weeks and there needs to be at least 33 days' notice of the referendum," he told Sky News.
He said voters did not appreciate "very long campaigns".
The prime minister said he had seen the 'yes' argument for the referendum pamphlet, describing it as a very strong case.
Mr Albanese brushed off polling showing support for the voice was plunging, saying he remained confident a majority of Australians will vote in its favour.
Newspoll shows national support for the referendum has dropped to 41 per cent, with 38 per cent of female voters and 45 per cent of men backing the constitutional change.
Support for the 'no' vote in the regions has grown to 62 per cent, with only 31 per cent in favour of the voice.
Australian National University marketing lecturer Andrew Hughes described the 'yes' campaign so far as disappointing.
"They've started off from an emotional perspective, rather than starting off logical and progressing to emotional," he told AAP.
Dr Hughes said there was time to get the campaign back on track but it needed to be done quickly.
"I do wonder if it is too late, I suspect they will kick off hard soon," he said.
Dr Hughes said the public wanted to see the detail, with people more distrustful of governments after the COVID-19 pandemic.
He said the campaign strategy was the wrong type to run in this context.
The marketing expert suggested the 'yes' camp could provide information about potential models for the voice.
The composition, powers, functions and procedures of the voice will not be laid out by the parliament until after the referendum.
Opposition Indigenous spokeswoman Jacinta Nampijinpa Price confirmed the 'no' campaign had submitted its case to the electoral commission for the pamphlet.
Senator Price said the essay produced a simple and clear message.
"My colleagues and I believe Australians deserve details, consultation and transparency - instead they've been given a rushed process and a proposal that is risky, full of unknowns and enshrines division in the constitution," she said on Monday.
Indigenous Australians Minister Linda Burney said drafting the official 'yes' case had been a collaborative process taking in the best arguments in support of the voice across the parliament.
"A voice is an idea many years in the making and many Indigenous Australians have put a great deal of hard work into achieving constitutional recognition," she said.
The Liberal-National coalition supports legislating local and regional voices, but not putting a voice in the constitution.
