He said he believed support for the Voice in the party room could be doubled if the wording of the referendum was changed.

“I want the best possible words to be presented and the evidence[on Friday] was that a number of constitutional experts agree that the words could be improved,” said Bragg,a longstanding supporter of a Voice to parliament and constitutional recognition.

“The better the wording,the better the chances of success. And by better,I don’t mean a Voice which is entirely neutered and can’t speak to the executive.

“There’s a column of support,I think,that could be unlocked if this proposal was de-risked ... I think you would double the group.”

Anne Twomey,a professor of constitutional law at the University of Sydney,told the inquiry on Friday that the wording could be amended to be more precise.

“I do not believe the High Court will draw the kind of implications people have said,” Twomey said.

“Could the wording be more precise? The answer is always yes. Do I have objections to it being more precise? The answer is no.”

Liberal members mobilising on WhatsApp

Hours after Dutton announced the party would oppose the referendum for an Indigenous Voice to parliament,some Liberal members were invited into a WhatsApp group entitled “Operation Valkyrie”.

Armed with a codename drawing inspiration from a failed attempt to assassinate Adolf Hitler,party members began canvassing how they could push back against the decision and campaign for the Voice.

Liberal MPs said they were never in the group.

It was one of multiple groups created on encrypted messaging service WhatsApp by Liberal members in the hours and days leading up to and followingDutton’s announcement.

There is a wider WhatsApp group that includes current and former MPs and staffers,where discussions on the upcoming steps are taking place.

Members of the group chat said it has a less contentious name than the 1944 plot to overthrow Hitler,which resulted in all the conspirators being executed.

‘Define our party for a generation’

The day before Liberal MPs went into the party room on April 5,their former colleague Fiona Martin sent some of them a text message urging them to be courageous.

“Good luck tomorrow. The outcome of tomorrow has the potential to define our party for a generation. Back yourself,be heard,” read the message from Martin,who lost her seat of Reid at last year’s election.

Martin told this masthead the Voice should have been above party politics,but many Liberals had decided to back an “American-style scare campaign” against the referendum instead.

“We have legal obligations through the UN Declaration on the Rights of Indigenous Peoples that Australia has supported since 2007,” Martin said.

“My job as a Liberal is to encourage members of my party to see and to highlight our obligations internationally,but also our moral obligations.”

Martin said the Liberal Party should be advocating for the Voice because “we are the party that wants communities to be able to do things independently”.

While the current group of MPs publicly supporting the Voice is small,Martin said she believed there would be a “domino effect” with more coming out onto the Yes side.

“I actually think the more Liberals that speak out and are quite vocal on this,the more likely that we will get other Liberals who are sort of thinking about it now to jump on board on this issue.”

Martin said there would definitely be a formal campaign of Liberals in favour of the Voice,but it would most likely be launched once the parliamentary committee finishes up next month.

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