The building workers' organisations are even disliked among supporters of Labor, which relies heavily on union donations to fund its election campaigns.

The leaked survey of 1000 ACT voters was conducted last month. Its findings have been circulating among Coalition figures and groups close to them.

The poll coincides with Prime Minister Malcolm Turnbull's attempt to capitalise on anti-union sentiment by threatening to dissolve the Senate if it blocked legislation to re-establish the building unions watchdog.

The Senate impasse may spark a double-dissolution election later this year, which would highlight the main parties' opposing stances on the need for an Australian building and construction commission.

The February survey asked respondents whether they had a favourable, neutral or unfavourable impression of a range of subjects, including construction industry unions such as the CFMEU.

About three times as many Canberrans (44 per cent) had an unfavourable view of the unions compared with those who had a favourable view (16 per cent) – giving a "net favourability" of minus 28.

A summary of results, seen by Fairfax Media, shows building workers' unions were far less popular among ACT voters than any of the main political parties. By comparison, the Liberals' overall favourability was mildly negative, Labor's was neutral and the Greens were mildly positive.

Dislike of the CFMEU and related unions was strongest among Liberal voters (net favourability of minus 62) and older Canberrans (minus 51). However, even Labor and Greens supporters (minus 8 each) were more likely to have a negative view than a favourable one.

CFMEU ACT secretary Dean Hall dismissed the polling as "self-serving" and designed to malign his union.

"If [the survey] had asked this question – 'Do you think the CFMEU is a strong union that delivers for its members, particularly in safety and better wages and conditions' – you'd probably get a situation where, even if people didn't have a favourable view, they'd believe the CFMEU was a strong union that stood up for its members," Mr Hall said.

"What I'd say to the Liberal Party, spending all its rich developers' and big-end-of-town money to run polls, is it would have been better if they'd asked some of the following questions if they really cared about the people of the ACT. 'Do you support the cuts to Medicare? Cuts to Gonski and school funding? $100,000 university degrees and getting rid of penalty rates?' "

However, the Masters Builders Association's ACT executive director, Kirk Coningham, said "militant unions" in his industry deserved their poor reputation.

"Just as builders don't want to be judged on the worst members of their industry, I think it's a shame the broader union movement is being judged on their worst in their industry," he said.

Mr Coningham said there were good unions in Canberra, such as those that represented public servants and nurses.

"They negotiate hard for their members and they impose the ultimate sanction [during disputes] of the lawful removal of their members' labour. I think everyone respects that," he said.

"But militant unions like the CFMEU have thuggery as part of their business model."

Mr Coningham said building unions escaped greater sanctions during the recent trade unions royal commission only as a result of "technicalities", because existing laws failed to adequately prevent industrial bullying and intimidation.

"I've spoken to at least half a dozen companies [in Canberra] that have deliberately stayed small – they've constrained growth – so as not to come on the radar of the unions, because they fear that, if they do, they'll be run out of the industry."

Polling by Essential Media last year found a large majority of Australians believed that unions in general (as opposed to construction unions) were important for workers.

About one in six ACT workers are union members, slightly more than elsewhere in Australia.