The parliamentary agency responsible for costing the policies of political parties has disowned modelling the Turnbull government used to attack Labor's tax plans.
Treasurer Scott Morrison on Monday leaped on so-called "independent modelling" of Labor tax policies by his own department and the Parliamentary Budget Office.
He predicted a "tax winter" for families and small business if Labor ever won government, warning of a $150 billion hit to the economy.
But the PBO wasn't keen to put its name to the unpublished modelling News Corp publications and Mr Morrison used to take aim at the opposition.
"References in the media this morning to modelling being released today by the Parliamentary Budget Office are incorrect," the PBO's Jenny Wilkinson said in a statement.
The agency said it released a post-election report on policy costings in August 2016, several weeks after the federal election.
Shadow treasurer Chris Bowen accused the treasurer's office of feeding the modelling to News Corp.
"Here we are barely a year into the parliamentary term and the treasurer of Australia is reduced to making up stuff," he said.
The modelling failed to take into account Labor plans to cut income taxes for low and middle-income earners.
"Watching Scott Morrison trying to add up numbers is like watching an episode of Survivor or Lost - it's entertaining, but couldn't be further from reality," Mr Bowen said.
Mr Morrison labelled as a "six shooter tax slug" Labor's planned taxes on family trusts, investment, housing, lifting the top marginal tax rate and "secret" superannuation taxes.
Mr Bowen responded with ridicule: "Looks like the treasurer has used his "six shooter" to shoot himself in the foot."
Opposition finance spokesman Jim Chalmers said there was a "mysterious absence" in Mr Morrison's claims of his own tax hike on low and middle-income Australians and the $21 billion in new taxes in the May budget.
