Opposition transport spokesman Mark Parton wants more scrutiny on light rail stage 2A after the Auditor-General recommended the business case be made publicly available.

"Despite the Auditor-General recommending the government make the business case publicly available, the Labor-Greens Government refuses to do so," he said.

"The report found several issues, with costs understated, benefits overstated and an extreme lack of transparency."

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In September 2021, Auditor-General Michael Harris found an earlier analysis failed to show how the rail line would be a catalyst for urban development.

Further to this in May 2022, the ACT government was warned "insufficient attention" was paid to an economic analysis for stage 2A of the light rail.

Mr Parton argued this had "denied Canberrans any meaningful insight into the project", finding the "lack of transparency ... mind-blowing", which in turn has inspired the expected motion on Tuesday.

Transport Minister Chris Steel has previously defended the benefits of the next stage of the light rail, saying ongoing commercial negotiations prevented the government from releasing updated costs immediately.

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