The territory's opposition formally pulled its support for light rail to Woden on Monday, claiming it would cost $3 billion to build.

However, the government has refused to say whether or not this assertion from the Liberals was correct or even a ballpark figure, citing ongoing procurement processes.

ACT Chief Minister Andrew Barr described the Liberals' position as "stale and conservative".

He said the government would release whatever information it could prior to the 2024 election, but this would not pre-empt the signing of any contracts, saying market circumstances would change.

"The information we are able to release ahead of the election in 2024 we will do so," he said.

"Infrastructure markets go through their peaks and troughs, there will be different types of infrastructure projects on the ACT government's agenda.

"As we get closer to procurement, we will clearly make more information available [but] what we're not doing is playing the rule-in-rule-out games or trying to condition the market to bid even higher for projects, particularly in the current infrastructure environment."

ACT Transport Minister Chris Steel said the government had shown an "unparalleled level of transparency" and would release further business cases for the light rail as they were developed.

But Mr Steel has also previously indicated the government was committed to light rail no matter what.

"The opposition has made it clear their timeline is to never deliver light rail down to the south side, to the inner south, Woden and Tuggeranong. They want to deny access to the same great public transport system and lifestyle that northsiders enjoy," Mr Steel said.

"This is the most significant infrastructure project in Canberra's history, we always said it would be more complex."

Light rail has been a signature policy for the territory government over the past decade. The first light rail stage, linking Gungahlin and the city, began operations in April 2019, following years of planning and construction.

The second stage of the light rail is being split into two parts. The first part, named stage 2A, is an extension from the city centre to Commonwealth Park and the second part, stage 2B, is from Commonwealth Park to Woden.

An audit of a 2019 business case for stage 2A of the light rail found it failed to show how the line would be a catalyst for urban development, which is a key expected upside for the project.

The opposition has put the estimated cost of light rail to Woden at about $3 billion. Liberals' transport spokesman Mark Parton said this analysis had been informed by views of consultants and people in the engineering community.

He said the route to Commonwealth Park would cost about $343 million, works on four bridges along the Woden route would cost about $325 million, the actual construction costs would be $1.3 billion, road changes would be $185 million, the cost of acquiring light rail vehicles would be $66 million and other associated costs would total $200 million.

There was also a 30 per cent variance taking into consideration inflation.

At the 2016 election, the Canberra Liberals fought hard against light rail to Gungahlin, however, this position changed in 2020 when the party committed to building the light rail to Woden.

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Opposition Leader Elizabeth Lee said the situation had changed, pointing to advancements in electric bus technology. She said the situation between Gungahlin and Woden was completely different as there were serious transport issues in Canberra's north prior to the construction of light rail.

She also said it could be another decade before light rail would reach Woden.

"Every election is about decisions and this is why the Canberra Liberals are coming out early. There wouldn't be many other oppositions across the country that come out at about midpoint to make sure that we are being as upfront with the public as possible," Ms Lee said.

"The best estimate that we have with the tram arriving at Woden is not for another decade at least."

Ms Lee said the Liberals would reinvest money marked for light rail back into schools, hospitals, roads and other front-line services. She claimed money had been ripped out of these services to pay for the light rail and Canberrans had seen the impact of this.

However, Mr Barr said the government needed to be capable of managing multiple large projects simultaneously, saying it was what an "experienced and mature" government does.

He said the territory had been the fastest growing Australian jurisdiction for the past 10 years with the population likely to reach 500,000 in five years. He said if the government did not make these investments the city would not be able to serve the growing population.

"The one thing I am certain of is that Canberra will continue to grow and if we don't make these investments now we'll cause ourselves even more pain into the future. If you're concerned about congestion now, if we don't make these investments we won't remain a 20-minute city," Mr Barr said.

Greens leader Shane Rattenbury described the Liberals' as being "out of touch" and "out of ideas".

"The Canberra Liberals have slammed the door on light rail once again," he said.

"Canberra faces real challenges in the future - congestion, climate action, urban sprawl - and the Canberra Liberals have no clear plan to address these issues. Whether they lack the foresight, the imagination or the fortitude, it is untenable for the Canberra Liberals to have no vision to address the reality of these challenges."

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