The Greens' plan to speed up the delivery of future stages of Canberra's light rail network is based on a "fantasy", the Transport Minister has said.
Chris Steel said different trades were needed at different stages of the project and it was not possible to roll on from one stage to the next in the way the Greens had proposed.
"This fantasy doesn't exist of just continuing on. Unless you're building in parallel, and we're constrained fiscally in our infrastructure to be able to do that, and we're realistic about that," Mr Steel told a forum organised by the Public Transport Association of Canberra on Monday night.
"But we can do one stage a decade. That's what we're working to."
Jo Clay, the ACT Greens spokeswoman on transport, said the Greens would push harder to deliver light rail faster, including a larger project team, more ambitious deadlines and implementing a rolling program of planning and construction.
"Infrequent and inconvenient bus services lock most people into the expense of having to own a car, and with so much private car travel, transport is the number one source of climate pollution in the ACT," Ms Clay said in a statement on Tuesday.
"We must improve public transport, and give Canberrans the light rail that they love."
Ms Clay told the forum a rolling program of construction would keep costs down because the workforce would be kept in place to work on different parts of the network.
"We think it is madness to plan a stage then stop and then build a stage then stop, and then go out and procure another stage. We actually should just have the workforce to be planning what we need and building it on a rolling program," she said.
The Greens also want to increase light rail services between Gungahlin and the city at weekends, during morning and afternoon peaks and on Friday nights.
Longer platforms that could support more carriages on light rail vehicles to expand capacity should also be investigated, the Greens said.
Canberra Liberals transport spokesman Mark Parton told the forum the LIberals were not ideologically opposed to light rail, but would cancel the extension from Commonwealth Park to Woden on financial grounds.
"I also think - and I'll get into trouble for saying this - I'm not sure that we're ideologically opposed to light rail. If we could wave a magic wand and just get it, yeah, I think it would be great," Mr Parton said.
"But we can't. We just can't. In part as a consequence of the pandemic and other matters, the cost of building stuff, whatever it is, has gone up remarkably and the cost of building this project continues to to rise to that $4 billion price tag that we've put on it. I think it will be exceeded quite remarkably."
The ACT government has declined to say how much the project to extend light rail from Commonwealth Park to Woden would cost, saying they do not want to prime the market before a tender process.
Mr Steel told the forum the costs would be "significant" but the project would deliver a significant benefit for Canberra for decades to come.
"We've been clear that we'll consider a business case next term and following the procurement, we'll release the business case and we'll release the final contract for the delivery of stage 2B," he said.
The 1.7-kilometre extension of light rail to Commonwealth Park is due to open in 2028, more than 8.5 years after the first stage opened between Gungahlin and the city.
Passengers would then be able to travel to Woden after construction on stage 2B of the project is completed between 2028 and 2033, the ACT government revealed in March.
