Former Coalition government minister Ken Wyatt has urged the Liberals to support the Indigenous Voice to Parliament or risk inflaming a "global perception" they are a "racist party".

In an exclusive interview with Guardian Australia the former Minister for Indigenous Australians said opposition leader Peter Dutton must allow the Liberals a conscience vote on the referendum, saying he knew of many who would back it "if given the chance".

Mr Wyatt, a Yamatji man who is a member of the government's Referendum Working Group, said he had not spoken to Mr Dutton about his views.

"No, and he hasn't contacted me either. It's a two-way process. But I engaged with Peter over time as a member of parliament. And that's all I'll say," he told the Guardian.

The former minister described Mr Dutton's persistent calls for answers to his 15 questions about the Voice process as a "smokescreen".

"I think if Peter was given the answers to the 15 questions in tablet form from Moses, he still would not accept them," Mr Wyatt said.

He noted that one of the 15 questions related to how governments would prove the Aboriginality of any members of the Voice.

"In this day and age, if you ask what percentage is an Aboriginal person? What is the percentage of an Aboriginal person's bloodline? Then it shows that we haven't moved forward," Mr Wyatt told the Guardian.

"I thought we'd got over those days. Having had those long fights over long periods of time to get rid of that type of legislation which use that wording. But we haven't, not when you ask that question."

Mr Wyatt believed it would be a mistake "globally" for the Liberals to not support the referendum, adding to a perception the party was "racist", citing incidents he had experienced as a minister under the Morrison government.

He said he was often asked 'How do you cope working in a racist party like yours?' while in government.

"It's not my perspective; it's a global perspective," he told the Guardian.

"So there is a perception about our party, which I am sad about, because the Liberal party is a good party, and there are a lot of good people within the Liberal party."

Last year Mr Wyatt told a WA Mining Club event that progress towards enacting the Uluru Statement from the Heart would be greater over the next three years than it would have been had the Morrison government been re-elected.

At the same event he noted that he had never discussed Mr Dutton's boycott of the Apology to the Stolen Generations with him.