The Parliamentary Budget Office has been forced to disown modelling released by the Turnbull government that claimed Labor's tax plan would put a $150 billion tax bill on families and small businesses.
On Monday, Treasurer Scott Morrison seized on the figures to claim that Labor's tax plan would hit retirees, businesses, negative gearers, and those benefiting from capital gains tax.
"There is a tax winter coming under Bill Shorten if he ever becomes Prime Minister," Mr Morrison told Sky News.
But in a rare public intervention, the independent office issued a statement that it had nothing to do with modelling released by the Treasurer's office on Monday morning.
"References in the media this morning to modelling being released today by the Parliamentary Budget Office are incorrect," said Parliamentary Budget Officer Jenny Wilkinson, referring to several reports in News Corporation publications.
"The analysis reported in the media this morning was not conducted by the PBO."
Shadow treasurer Chris Bowen condemned the "blatant politicisation of the independent Parliamentary Budget Office."
"Scott Morrison needs to withdraw his ridiculous claims about Labor's tax policies and apologise for seeking to politicise the independent PBO," he said.
Reporters were briefed by the Treasurer's office on Sunday that proposed Labor taxes, including a $65 billion hit to small businesses and a $15 billion slug on family trusts, were costed by the PBO and Treasury.
On Monday, the PBO said the last time it had assessed Labor policies was in August 2016 as part of its role costing policies taken to the election. Its rules forbid it from costing the polices of one side of politics at the request of another.
The Treasurer's office confirmed that it took the PBO figures prepared after the 2016 election and moved them forward one year. As a result, what was presented as the "true toll of Labor policies" excluded more recently promised tax cuts including to the Coalition's proposed increase in the Medicare Levy.
Labor has not announced its position on the company tax cuts for small businesses but the Treasurer's office claimed its $56 billion costing of Labor's position on company tax was a "Treasury costing".
Asked whether the Treasury had costed the opposition's tax policy as claimed, a spokesman for the Treasury declined to answer and referred the question to the Treasurer's Office.
In 2012 when Labor distributed a "Treasury costing" of the Coalition's policy on parental leave, the Coalition's Joe Hockey wrote a letter of complaint to the Treasury secretary Martin Parkinson.
Dr Parkinson replied it had "long been the case" that the Treasury was periodically asked to cost alternative policies.
Outside the caretaker period before elections, it did not conduct costings unless specifically directed to.
In The Age and Sydney Morning Herald