Referendum working group member and Uluru Statement advocate Thomas Mayo says Opposition Leader Peter Dutton's comments to the media are "disappointing" and do not reflect what he said when he met with the group.
Mr Dutton attended his first in-person meeting with the group in Canberra on Thursday alongside Shadow Minister for Indigenous Affairs Julian Leeser.
Sources told the ABC that during the meeting Mr Dutton said he supported constitutional recognition for Indigenous people and a version of an Indigenous Voice, and acknowledged there were systemic and structural problems with closing the gap that must be addressed.
But on Friday Mr Dutton told the media he did not believe the referendum would be successful.
"I think the Voice is not going to get up," he said.
"I don't think its going to be successful and that's because the prime minister has had this half-hearted effort in relation to not explaining the detail, not being across the detail."
Speaking with the ABC's Afternoon Briefing, Mr Mayo said that was not what Mr Dutton said during the meeting.
"He (Mr Dutton) said that they continue to support constitutional recognition. They said that our Voice is good policy, it's an important thing to do and they supported it when they were in government," Mr Mayo said.
"It's disappointing to have those discussions inside the room and then to hear that afterwards.
"I think it comes to a point where you have to question, is this about the best thing to do for the country and for Indigenous people or is this about politics?"
Indigenous Australians Minister Linda Burney urged Mr Dutton and the opposition to keep meeting with, and listening to, the working group.
"I say to Mr Dutton, please stay engaged with the working group. That is certainly the desire of the working group," she said.
"I just believe that it's important that all parliamentarians engage with his process and come to understand it."
Ms Burney was not present when Mr Dutton met with the working group.
"Unfortunately, I was asked to leave the room by Mr Dutton, so I wasn't actually there to hear what he had to say," Ms Burney said.
Mr Mayo said the group discussed with Mr Dutton why some of the details he had been asking for would not be decided until after the referendum.
"If all of that detail was put before the referendum, then Australians would think that that is what they're voting for," he said.
"There's an understanding that to put all of the detail at the front of the referendum before people vote is actually problematic."
Mr Mayo believes the working group is close to gaining the support of the opposition.
"I think that it indicates that we are quite close, I think as far as the understanding that this is the best thing to do, that this should be supported," he said.
The working group also discussed the wording of the question and the constitutional amendment, and what the official name for the proposed body would be.
Mr Mayo said the group was looking to finalise the wording as soon as possible.
"There is [sic] timing matters about when a referendum alteration bill needs to be tabled and we are working with urgency," he said.
"We're making sure that we make the best decisions so that the Australian people can be confident that this is something that they can support."
The ABC has contacted Mr Dutton's office for comment.
