The Joint Standing Committee on the National Capital and External Territories published its report on the territory government's plan to send the tram from Civic to Woden on Monday.

It has indicated it is likely to make the territory seek further approval before giving the final go ahead because the ACT government's proposed route is partially inconsistent with the National Capital Plan.

It also warned the government's proposed route would "unavoidably add further complexity, time, and cost to the project".

The National Capital Plan allows for an intertown public transport system along Kings and Commonwealth Avenues and State Circle but not to cut across the Parliamentary Triangle, like the ACT government's preferred route does.

Transport Canberra officials told the committee the government had chosen to take light rail through Parkes and Barton as it would pass more employment hubs and cultural institutions, meaning more people would use the system.

Transport Canberra director-general Emma Thomas told the committee the other more direct route "was not actually the easier or cheaper route, because it goes so close to Parliament House and because there are more bridges involved and there are greater difficulties in providing pedestrian access to the light rail system".

She also referenced a survey from last year that showed 75 per cent of the 4437 respondents preferred the Barton alignment to one that travelled past Parliament House onto Adelaide Avenue.

However the National Capital Authority told the committee the National Capital Plan, which could be considered as "in-principle" approval for light rail routes, did not cover Barton.

It warned that any route that wasn't covered by this plan would "require information that is much more detailed than that which appears to be currently contemplated by the ACT government before a decision could be made".

Committee chairman Ben Morton, a Liberal MP, said the ACT government could still choose to use the Barton route, and any suggestion this prevented them from doing so was "ludicrous".

"However, should the ACT government choose to pursue a route alignment that is only partially consistent with the National Capital Plan, this will unavoidably add further complexity, time, and cost to the project," he said.

"The committee has recommended that in that case, the ACT government should work with the National Capital Authority to ensure Commonwealth approval of the route, by amending the National Capital Plan. This should be done before undertaking the full works approval application and other Commonwealth approval processes."

The report said if the ACT government remained committed to its proposed route, there would have to be a two-stage Commonwealth approval process.

"The first stage would comprise working with the NCA and other relevant Commonwealth agencies to definitively determine whether the proposed route is feasible. The NCA has advised that this would require the ACT government to provide the results of an initial rapid heritage assessment," it said.

"It is only after these matters have been addressed and the proposed route has the approval of the Commonwealth, that the second stage should commence."

The second stage involved works approval and other Commonwealth approvals.

"The committee is concerned that if the ACT government chose to invest in the development of detailed designs, heritage assessments, and an Environmental Impact Statement without prior Commonwealth approval of its proposed route alignment, there is a significant risk that this investment could be wasted," it said.

Mr Morton said the committee wanted to ensure the simplest possible Commonwealth approval process for the light rail project.

"It is not the committee’s intention to slow or hinder the approvals process, but rather to provide certainty for the ACT government and the people of Canberra, and to ensure that time and money is not wasted pursuing a route that is not endorsed by the Commonwealth and therefore not feasible," he said.

The report noted the authority's concerns that the project had "not adequately demonstrated sensitivity to the importance of the central national area or parliamentary zone".

"The development of light rail amenity must not come at the cost of the long-term character and heritage of the national capital area and the parliamentary zone," it said.

Transport Minister Meegan Fitzharris told ABC Radio this was not the end of the Barton dogleg and government would apply for the National Capital Plan amendment.

"We've always known this route requires this amendment," Ms Fitzharris said.

She said variations to the plan were "by no means unique" but the challenge for the project going forward would be getting the federal minister and federal parliament to make a "timely decision".

However Mr Morton said it was not certain the ACT government would get the amendment approved.

The Public Transport Association of Canberra said the two-step approval process was "the most appropriate way forward" and the report provided "much-needed certainty" for the project.

The committee also said the ACT government appeared not to be heeding the advice of the NCA on the need for wire-free running through designated areas.

The current proposal features wire-free running from Alinga Street to Sydney Avenue, and again in Woden from the Phillip Oval stop to the Woden Town Centre.

The NCA told the committee it had advised the ACT government that these designs are not consistent with the previously stated requirement.

However the government said the use of overhead wires and poles in some designated areas would be unavoidable due to the limitations of existing technology.

"Due to the curves and gradient, traffic intersections, and the distance between the stops, the Sydney Avenue to Hopetown Circuit section may require more energy than can currently be stored on board the LRVs [Light Rail Vehicles] using technology available today," the government said.

Nevertheless, the committee has recommended there be no poles and wires on Commonwealth Avenue, Kings Avenue, State Circle, Brisbane Avenue, Sydney Avenue, Canberra Avenue to Manuka Circle, Hobart Avenue, Melbourne Avenue and Adelaide Avenue to Kent Street.