Unions ACT believes recent polling proves a majority of Canberrans strongly supports light rail, despite leaked briefings revealing concerns the Liberals were "winning the referendum".
An online survey of 1014 Canberrans, commissioned by Unions ACT, found 55 per cent of respondents were strongly in favour of the $783 million project with 27 per cent strongly opposed.
Another 83 respondents said they were somewhat supportive (8 percent), while 73 respondents (7 percent) said they were somewhat opposed. Only 27 respondents (3 percent) identified as undecided.
The survey, conducted between July 1 and August 28, asked respondents: "On balance, do you support or oppose the construction of a light rail system in Canberra."
Unions ACT secretary Alex White said the online poll proved there was a range of strong opinions about light rail, although opposition was strongest among conservative voters.
Mr White, who would not disclose the cost of the online polling, said qualitative questions revealed most support was based on perceived public transport benefits.
The results are a contrast to briefings on recent polling, leaked to the Liberals, that contained worrying signals for Labor as it prepares to sign contracts on the project.
The union polling of 1446 Canberrans was done in May but Unions ACT released only some of the results.
The full polling and some of Unions ACT's conclusions were leaked to Opposition Leader Jeremy Hanson, including a warning the tram is a "potential vote-changer", and the "Libs are winning referendum".
The May polling asked voters whether they would be more or less likely to vote for a candidate who supported light rail.
Forty per cent said they were less likely to vote for a pro-tram candidate; 32 per cent were more likely. Among Labor voters, 23 per cent were less likely to vote for a candidate who supported light rail.
But Mr White said the latest online poll proved public opinion had "turned sharply" thanks to campaigning, including automated telephone messages in Weston Creek and Woden Valley.
Chris Cooper, a Unions ACT organiser and the co-ordinator of the Fair Go for Canberra campaign, said the results were encouraging for proponents of light rail.
"From the survey results, it is apparent that the Canberran community wants a more efficient transport system and decongested roads, and a more sustainable city that will come with the construction of light rail," he said.
"We recognise that a small but vocal section of the community do not support light rail, and we will work with the community to help demystify some of the misinformation surrounding the project."
Opposition transport spokesman Alistair Coe said it was difficult to determine the legitimacy of the polling and was concerned Unions ACT appeared to be campaigning for the government.
"I have no doubts many Canberrans like the concept of light rail but when you look at the detail of what the government is going ahead with, there is reason to worry," he said.
"The question is whether this is the best way to spend $783 million, and we would argue there are far better things we could spend this on across the territory."
Unions ACT is expected to conduct more opinion polls on light rail in coming months, despite the Canberra Liberals objecting to its perceived campaigning on behalf of the government.
"We think it is disappointing that Unions ACT is spending workers' hard-earned money on a poll to top up the Labor party," Mr Coe said.