This week, the Australian Bureau of Statistics began posting out 16 million surveys asking enrolled voters to answer yes or no to the question “should the law be changed to allow same-sex couples to marry?”. 

Many polls have so far shown that the result will be in favour of the yes vote, but Dr Bonham said this was not definitive.

“What people say in polls about how likely they are to vote can’t really be trusted,” he said. 

“The turnout will be nowhere near 100 per cent, how high it will be is debatable.

“Some people are estimating half, some people are estimating two-thirds – there’s really no way to know.” 

Dr Bonham said that in postal votes in the past, there had been an age-based skew with older voters more likely to hand back their survey forms, but he said this may change. 

“I think this is an issue where it’s not so clear what will happen because it’s an issue that’s very important to a lot of young people,” he said. 

“I suspect that there will be a yes vote but I don’t want to be too confident about that because of it being a new thing.” 

On Tuesday, Police Minister Rene Hidding said he would undertake a “detailed log” of all events, media releases, opinion pieces and letters to the editor relating to same-sex marriage issued by the no vote and compare it to overall coverage. 

“We have already seen some alarming evidence of outright bias,” Mr Hidding said. 

“I will be scrupulously compiling and I look forward to providing the results to the Tasmanian people publicly after the close of the survey period.” 

But in Parliament on Wednesday, Opposition deputy leader Michelle O’Byrne questioned whether this would interfere with the performance of Mr Hidding’s current duties and whether he would use taxpayer-funded staff to complete the task. 

Mr Hidding said it was a personal commitment that he had made. 

All enrolled Australian voters should receive their survey forms by September 25, with the result to be announced by the ABS on November 15.