Chief Minister Andrew Barr voiced support for a "compromise" route for the light rail to get from Civic to Woden, after a federal parliamentary committee found the government's chosen course through Barton would likely lead to time delays and cost blowouts in getting the project approved.

Instead, the light rail could use State Circle to go south, a route that sits between the two options that were voted on by the public earlier this year - the Barton dogleg and a more direct route via State Circle.

State Circle was investigated as an option to send the tram to Woden by consultants at least three years ago, although it's unclear why the route was spiked.

It was also highlighted in the joint standing committee's report as a pre-approved route for inter-town public transport under the National Capital Plan.

As a Parliament House moral rights holder, Mr Guida was interviewed by the consultants looking at prospective routes, and said a tunnel behind the exposed stone wall on State Circle - and the cost penalty that it would involve - was part of the discussions.

"We talked about the potential then of having underground stops connected to the Parliamentary Triangle through lifts that might arrive where there's currently car parks, so the idea is you would tunnel behind the stone wall and have stop points where you'd rise up to Federation Mall," Mr Guida said.

While they would have to be careful about how close the tunnel was to the stonewall, Mr Guida said it would not be impossible to build it.

"What I would say is it's probably worth exploring to see what the benefits and liabilities are of that approach to make an informed judgement as a comparison of the other options that have been put forward. Leave no stone unturned," Mr Guida said.

"I don't have an opinion one way or another until I see a development proposal and that's not what I saw a few years ago. They were scouting concepts and issues that arise around them."

Mr Barr on Monday described the State Circle route as the "path of least resistance" in getting the second stage of light rail approved quickly, although stressed on Tuesday the Barton route was still a live option.

"We can have all the debates we want about preferred routes but in the end the preferred route is determined by the Commonwealth Parliament," Mr Barr told ABC Radio.

"[The Barton route is] still on the table but obviously we’ve been advised that would require a lot more work and potentially a lot of additional cost without a guarantee of approval," he said.

"Whereas if we have an in-principle approval for a State Circle alignment but we continue to work through these issues, we’re not going to make a decision until after the federal election and we see the final makeup of the new federal parliament because that will have big implications for our capacity to secure the support we need in the House of Representatives and the Senate."

Mr Barr said they would have to look at the final details at where the stops would be located to determine if the State Circle route would work.

"Where they're located will determine our capacity to make a State Circle alignment work well but necessarily in all of these considerations will be a series of compromises and trade-offs between a variety of competing interests and outcomes, not least of which is the capacity to get a project approved by the federal parliament because in the end this is Commonwealth land that requires the Commonwealth parliament to approve it," Mr Barr said.

Griffith University transport expert Dr Matthew Burke said the change in route could mean a cost saving.

Early estimates have placed the cost of the second stage of Canberra's light rail network at between $1.3 billion and $1.6 billion.

"If they move to State Circle and in particular build one less station it might actually expedite the project in terms of approvals and so we could see light rail stage two up quicker and so there's savings in both time and cost could be realised with this change," he told ABC Radio.