The federal Labor opposition is demanding that Treasurer Joe Hockey release the national commission of audit’s interim report into the operations of the commonwealth government as a Senate inquiry concluded the commission’s process was “rigged”.

Pointing to a News Limited story on Wednesday that said the commission’s 900-page interim report has been in Mr Hockey’s in-tray since Friday, shadow treasurer Chris Bowen and Labor finance spokesman Tony Burke said it was time to end the secrecy.

They said Mr Hockey, who is in Sydney preparing for this weekend’s G20 meeting, should make good his promise to release the report to the public.

“This report represents 900 pages of wrong priorities and nasty cuts we weren’t told about before the election,” Mr Burke said in a joint statement.

Mr Bowen said an open and transparent decision-making process based on the commission’s report was important.

“This issue demands enough time for the Australian people to consider the report’s recommendations and for an informed parliamentary debate,” Mr Bowen said.

In a separate statement, Australian Greens senator Richard Di Natale said the audit was a prop for the Abbott government to justify “cruel” spending cuts.

Senator Di Natale, the chair of a Senate select committee inquiry into the the process of the audit, released the committee’s first interim report on Wednesday.

“The Abbott government has constructed very narrow terms of reference for the commission and hand-picked ideological allies as commissioners so that it gets precisely the outcome it wants,” Senator Di Natale said.

“Tony Abbott has picked the players and written the rules so that the game was rigged before it even began.”

The commission is led by Business Council of Australia president Tony Shepherd.

The senator said the committee found the economic assumptions that underpin the commission’s terms of reference were flawed, and that its mandate was to just look at spending cuts.

“The bulk of evidence to the Senate committee indicated that government spending was stable. If there is a problem with the budget it is largely a revenue problem,” he said.

The commission is due to release its final report at the end of March and its recommendations will be used to form Mr Hockey’s first budget in May.