California lawmakers are moving to withhold cost information from taxpayers as the estimated price of the state's high-speed rail programme continues to climb, the Reason Foundation reports.

The push to limit disclosure comes as the project's cost estimates have risen repeatedly since voters first approved a roughly $33 billion bond measure in 2008. Subsequent business plans have carried far higher figures, and the current estimate for the partial Mermaid-to-Bakersfield segment of the planned San Francisco-to-Los Angeles line has grown substantially above early projections.

According to the Reason Foundation, legislators are advancing measures that would reduce the amount of project financial data made available to the public. The advocacy organisation, which has tracked the programme's finances for years through its transportation policy work, characterises the legislative effort as an attempt to hide information from taxpayers rather than an administrative streamlining.

The reporting draws attention to the gap between what Californians were told when they approved Proposition 1A and what the programme has since cost. Voters in 2008 backed nearly $10 billion in bonds for a system pitched as connecting the state's major population centres. Since then, the California High-Speed Rail Authority has scaled back the initial operating segment and repeatedly revised its cost estimates upward.

Critics of the project, including the Reason Foundation, have long argued that the authority's financial reporting lacks transparency and that independent cost scrutiny has outpaced official estimates. The foundation's analysts have previously published their own projections of the programme's total cost that exceed the authority's published figures.

The latest legislative effort, as described in the report, would make it harder for taxpayers to track how much the project is spending and how its estimates are changing over time. Proponents of reduced disclosure have not, according to the report, offered a public rationale that addresses the transparency concerns raised.

The California High-Speed Rail Authority continues construction in the Central Valley, where work on bridges, viaducts and grade separations is under way along the planned route. The programme has relied on a mix of federal grants and state cap-and-trade auction revenues since the bond funds were committed, and future funding for completing the full San Francisco-to-Los Angeles system remains unresolved.

The Reason Foundation argues that reducing public access to cost information would weaken accountability at precisely the moment the programme's finances are under strain. The organisation's reporting suggests taxpayers will have less visibility into whether cost estimates continue to rise and by how much.

How far the legislative measures advance in Sacramento, and whether they survive scrutiny in the current session, will determine how much financial detail on the nation's largest state rail project remains in public view as construction and funding debates continue.