"We need client input in the question design to ensure the research answers all of the questions and issues they need to know about," company director Grant Piazza said.

"Piazza Research rejects questions that we assess as misleading or biased or that do not provide sufficient context for the respondent to understand what they are agreeing or disagreeing to. The research process itself is guided by the research purpose set by the client during the project establishment phase."

He was responding to news this week that Capital Metro had a hand in devising questions for the government's tram polling in June last year, with follow-up polls also held in December 2014 and August 2015.

Comparison of Piazza Research's suggested questions and the final set of questions approved by the government shows the government's emphasis on the tram as way of creating jobs, improving Northbourne Avenue and encouraging a healthier lifestyle.

But any suggestion that Piazza Research was "removed from the process" was false, Mr Piazza said.

"Questions are always designed with our clients' involvement, but they must meet formal research standards otherwise they are disallowed," he said.

"We need client input in the question design to ensure the research answers all of the questions and issues they need to know about. Piazza Research rejects questions that we assess as misleading or biased or that do not provide sufficient context for the respondent to understand what they are agreeing or disagreeing to."

The research had been guided by the government's goals of testing awareness of the tram and support for it over time, examining new issues as they emerged, and testing and identifying messages and themes important to the community.

"This is a part of the survey designed to test messages and benefits to the community," Mr Piazza said. "It is OK to test new messages over time – this is a communications and support level survey after all..

"Many of the benefits tested in the survey actually came from community members in six community focus groups held with residents across Canberra. Inclusion of these benefits in the survey allowed us to test whether or not the benefits mentioned by community members in the focus groups were widely held (or not) across the broader community with statistical accuracy."

One of the questions was:

"The current trees along Northbourne Avenue are reducing in number due to poor health and weather impact. Building light rail along Northbourne Ave may mean replacing the current trees with new and longer-lasting trees. Do you support this approach?"

Sixty-nine per cent of respondents answered "yes".

Mr Piazza said the question was not written with "an agree-type response" in mind.

"The question was actually written to ensure the public were aware of the context of the situation in order to make an informed decision. It would be false to say, for example, that all the trees on Northbourne Ave are in good condition. The current condition of the trees is an important fact to communicate so the public can decide whether they support tree removal or not."

The draft and final questions were released to the Liberals under a freedom-of-information request, and Liberals deputy leader Alistair Coe has accused the government of "recklessly misusing taxpayers money as they scramble to create the facade that light rail is popular with Canberrans".

"If the government is so confident that light rail is worth the billion-dollar price tag, why would this polling be necessary to begin with?" Mr Coe said.

The surveys cost about $29,000 for the first and $27,000 for each of the follow-ups.

They show little movement in support for the tram over a year, with 55 per cent support in June 2014, 54 per cent in December 2014 and 56 per cent in August 2015 – the difference being well within the 2.8 per cent margin of error.