The federal government has not done any modelling on the impact of the Fair Work Commission's decision to cut penalty rates, responses to a Senate hearing have revealed, despite Prime Minister Malcolm Turnbull throwing his weight behind the cuts.
In answers to questions on notice from Senate estimates to be released on Friday, Treasury said it would assess a range of policy decisions when reviewing forecasts for the upcoming May budget.
"But this would not entail a specific modelling of the Fair Work Commission recommendation," a statement from its macroeconomic division said.
"There are likely to be some positive employment effects from a reduction in penalty rates, though it is difficult to quantify the precise effect."
The Fair Work Commission's decision could see wages slashed for thousands of Australians who work on Sundays in the retail, fast food, hospitality and pharmacy industries, as penalties fall from between 200 and 150 per cent from July.
Labor claims the decision would affect more than 600,000 workers, while the government says the number of people who regularly work on Sundays is closer to 285,000.
The Australian Industry Group has long pushed for the change, claiming rates are are too high, do not reflect the community standards of a 24/7 economy and force businesses to close on weekends.
In March, Mr Turnbull offered his first public economic support for the decision, saying he agreed with the view that the reduction in Sunday rates would lead to more employment opportunities.
In a submission to the Fair Work Commission, the government urged the economic benefits of the rate cut be delivered quickly, while taking into account potential impacts on employees and "some technical issues". It agreed the new rates should be phased in "over two years, possibly longer, but not as long as five".
Shadow treasurer Chris Bowen said the response from Treasury meant Australians could comfort themselves in the knowledge the government "has absolutely no idea" what the economic benefits are.
"Meanwhile, Malcolm Turnbull expects the same low- and middle-income earners who will experience the penalty rate cut to pick up the tab for the government's handout for big business," he said.
The government has also refused to outline the economic impact of the company tax cuts package it passed in March after a deal with Senator Nick Xenophon.
Mr Turnbull has said the company tax to businesses turning over up to $50 million would deliver "substantial economic growth", but has never quantified the actual contribution to GDP.
A preliminary analysis by the Grattan Institute found the $24 billion company tax cut would boost the economy by less than 0.2 per cent when fully implemented over the next decade.
"That translates into an increase of up to $3 billion in national income each year by the time the full effect has come in," the analysis found.
Employment Minister Michaelia Cash has been contacted for comment.
