Chamber executive Robyn Hendry said on Wednesday she was concerned that cancelling the contract – a key feature of the Liberals' election campaign – would hurt the territory's ability attract investment.

"It is important to ensure major infrastructure projects bring significant return to the economy and support creation of local jobs and economic diversification," Ms Hendry said.

Treasury has estimated the cost of cancelling the contract at between $220 and $280 million, although the Liberals say forging ahead with the project would saddle future generations with debt.

The criticism prompted a stern text message from Mr Hanson, who described Ms Hendry's statements as untenable. But the text was erroneously sent to Labor leader Andrew Barr's chief of staff, Jamie Driscoll, and Greens leader Shane Rattenbury.

"Given the chamber is funded for millions by the ACT Labor / Greens Coalition, particularly for a project we oppose and this is a significant issue at this election I believe the Business Chamber commenting on political parties and policies at this election is untenable," Mr Hanson said.

"I wouldn't want the reputation of the chamber to be damaged."

The 12-kilometre tram line from Gungahlin to the city will cost ACT taxpayers $939 million in today's dollars, including operations, capital and financing.

Ms Hendry's concerns have been repeated by ACT Engineers Australia manager Keely Quinn, who said cancelling the contract would have "considerable repercussions" for investment and business confidence in Canberra.

"The private sector wants to feel confident that their investments in Canberra will be secure," she said.

Consult Australia, an industry association group representing consulting companies, has called on Canberra politicians to honour infrastructure contracts, saying cancelling them would set "a dangerous precedent" and damage long-term planning.

In a letter to Professionals Australia ACT director David Smith, a union leader who represents public sector engineers and technicians, Mr Barr described the Liberals' position on light rail as "economic lunacy"

"The Canberra Liberals' decision to highly politicise investment in infrastructure does a significant disservice to Canberra's reputation," Mr Barr said.

Deputy Opposition Leader Alistair Coe has raised the prospect of having the light rail consortium, which includes German rail giant Deutsche Bah, build health and education infrastructure rather than light rail.

"If elected, a Canberra Liberals government could exercise the terminate for convenience clause or seek to re-scope the contract into worthwhile infrastructure," he told the Canberra Times earlier this year.

While critical of the Liberal's policy on light rail, the business chamber did not endorse any particular party and said there was bipartisan support for many initiatives discussed during the campaign.

Ms Quinn praised Labor and the Liberals for pledging to appoint a chief engineer to advise the government on major infrastructure projects and workforce planning.