Canberra's newly-christened light rail system could be stuck north of the lake a lot longer than expected, after the Coalition's shock federal election win upset ACT Government plans to get the project's extension to Woden fast-tracked.

Key points: ACT Government was hopeful Labor would fast-track the project

ACT Government was hopeful Labor would fast-track the project Stage two of light rail requires approval from Federal Parliament

Stage two of light rail requires approval from Federal Parliament Promise of $200 million from Labor fails to materialise

The ACT Government will also have to dig deeper into the territory's budget to fund light rail stage two, with a $200 million commitment from federal Labor now nullified.

Chief Minister Andrew Barr said he was disappointed by the Coalition win, and that he was unsure whether the project would be given the green light in this parliamentary term.

"It's going to set back the timeframe, there's no doubting that," he said.

"Had the election result gone differently on Saturday I was hoping to sit down this week with an incoming Labor infrastructure minister and an incoming Labor territories minister to get on with fast-tracking that project.

"It will now take a lot longer."

Unlike light rail's first stage, the extension to Woden would require the approval of Federal Parliament, because the two proposed routes would go through land owned by the Federal Government.

"Depending … on the final outcome of the Australian Parliament in terms of the Senate and the House of Reps, it may not be possible to get parliamentary approval for the second stage in this parliamentary term," Mr Barr told ABC Radio Canberra.

"But if we are unsuccessful in that regard, just simply on the parliamentary approval, then we will have to rethink our approach and the timeframe.

"What I won't do is waste everyone's time if they clearly say no."

Labor has not revealed a cost for stage two, and said it was not able to do so until construction details had been finalised, but recent estimates placed it as ranging from $1.3 billion to $1.6 billion.

Labor promised to foot $200 million of the cost of building stage two of light rail. ( Picture: Gregory Nelson )

Mr Barr said the Government would now have to forego the funding promised by Labor if it won government.

"We will look to manage that within ACT resources, but of course it now look as if the project will fall outside of the next three-year federal term," he said.

No blank cheques: Opposition Leader

ACT Opposition Leader Alistair Coe said the re-election of the Coalition meant that the ACT Government's plans would now be subject to more scrutiny by both the House of Representatives and the Senate.

"The composition of those chambers is going to have an impact as to whether that approval comes forward," he said.

"But … it's going to depend on whether the ACT Labor Government can mount a good case as to why stage two of light rail is necessary.

"I'm sure if they make a good case they'll have no trouble convincing members on both sides of both houses."

Mr Coe said federal Labor's $200 million in promised assistance had been motivated by politics rather than an analysis of the costs and benefits.

"The federal Liberal Government is not going to go giving blank cheques to any state or territory government, let alone the ACT Labor Government," he said.

"So if the ACT Labor Government wants to get investment from the Commonwealth in stage two of light rail they're going to have to present a good economic and financial case for that investment.

"To date we haven't seen it. Where is the business case for stage two? Nobody knows."