Federal Labor has hit back at LNP criticism of cost blowouts and time delays to Snowy 2.0 with a reminder that it was a Coalition government that first signed off on the much maligned mega-project nearly 10 years ago, based on infamously off-target “back of an envelope” calculations.

Federal Parliament’s Senate Estimates committee on Tuesday night received a progress report on Snowy 2.0 that told of a “significant milestone” in the tunnel-boring department, but offered no updates at all on how much further the project’s now $12 billion budget might have blown out.

Speculation has been rife over what will be the outcome of the “line by line” reassessment of costs Snowy Hydro requested from its main contractor in October last year – and which the contractor rather ominously said would take nine months to complete.

A report in The Australian last month cited the latest modelling from experts based out of the Victorian Energy Policy Centre that has estimated a final price tag for Snowy 2.0 of $42 billion, factoring in the added costs of interest and connecting the project to the grid.

Speaking at the hearing, Snowy Hydro chief Dennis Barnes dismissed the $42 billion figure as “completely conflated with transmission costs and interest costs which we have never claimed to be part of this project.