Thomas Mayo and Kerry O'Brien tell forum in Blue Mountains that Voice to Parliament referendum can still be won

That was the message delivered to a packed Blue Mountains Theatre audience in Springwood on Saturday, September 2.

"Yes" campaigner Thomas Mayo urged supporters to sign up as volunteers in order for the referendum to succeed on October 14.

"We need people to join the 'Yes23' campaign... This is an invitation to all Australians. We're not going to win it unless you get engaged," he said.

Mr Mayo, a signatory to the Uluru Statement From the Heart and co-author of 'The Voice to Parliament Handbook', was joined by former ABC presenter Kerry O'Brien at the forum.

The pair were asked about media commentary that the referendum was already a lost cause.

Mr O'Brien said he believed that "cautious optimism is well founded" for a "yes" outcome despite waning support in opinion polls.

"My informed suspicion is that these polls are not adequately testing a proper diversity of public opinion... But we would be fools to ignore the trend, which has been down," he said.

"In a way, the 'no' campaign got out of the blocks faster. They were going straight for the jugular from the outset... I think it was always going to take time for the 'yes' campaigners to hit their straps and for people to begin to switch on."

READ MORE:

The veteran journalist said simple acts like wearing a "yes" badge or t-shirt, or placing a "yes" corflute outside your home, can make a difference.

"It might sound improbable, but events like this and people like you are going to be one of the very significant factors in why we end up with a 'yes' vote," he told the audience.

Mr Mayo said having "respectful" conversations with people about the referendum can change minds.

"But we are running out of time so get started immediately," he said.

The pair took aim at factually inaccurate claims made by the "no" campaign.

"We are a democracy and people have a right to take this position or that position but we also have a right, on such an important issue, to know the truths," said Mr O'Brien.

"I ask the question - if you are so convinced and so confident that you are right in urging people to vote 'no', why do you sometimes have to engage in lies to bolster your arguments?"

Responding to specific "no" claims, Mr Mayo said the Voice to Parliament would not cede Aboriginal sovereignty, a position backed by Indigenous and non-Indigenous experts.

When asked how the Voice to Parliament would impact calls for a treaty, he said this was separate matter and that the "treaty first" argument "doesn't make sense".

Treaties negotiations are already underway in most states, he said, but it is a complex process that experts agree takes decades.

"Why would we wait an unknown amount of time for an unknown outcome?" he said.

Mr O'Brien said criticism about a lack of detail on the makeup of the Voice to Parliament was unfounded.

He said the Constitution wasn't meant to be a detailed document "that says 'how many this or how many that... or how it will function'." This detail will rightly be scrutinised by both houses of parliament where our elected representatives reside.

Mr Mayo described the Voice to Parliament as an "incremental step forward" that "provides us with the means to see better outcomes".

He said non-Indigenous Australians would not "lose anything" by supporting it.

"But we're going to gain over 60,000 years of continuous heritage and culture - something that we all share - and we're going to do it in a way that closes the gap [between Indigenous and non-Indigenous Australians]."

"If you have a voice, you're able to do better. That's a no-brainer," he said, citing setbacks for Indigenous people when previous bodies have been abolished.

Mr O'Brien said an Indigenous advisory body to government would only have benefits.

"When Indigenous people are heard on policy issues that are going to affect their lives, the policies are better and more efficient, the policies get better outcomes, the money is spent more wisely, the money is less likely to be be wasted. That is where the benefits lie for all of us," he said.

Mr O'Brien said the outcome was just as important to non-Indigenous Australians "because we've all got the same investment in the end".

"We want a healthy, unified nation. We want a nation that we can stand up and feel proud of," he said.

Mr Mayo tempered his support with a warning that the referendum was a "once in a lifetime" opportunity.

"We get one shot at this," he said.

"We've talked about what we gain if we succeed but if we lose, it's not just the status quo [that is preserved]... It will take us backwards if we fail. I believe that we can win because I have faith in the Australian people but you've gotta do the work, so let's get out there and do it."

The event was hosted by Blue Mountains Unions and Community.