The tenure of the incoming Treasury secretary, Philip Gaetjens, could run for less than a year after opposition treasury spokesman Chris Bowen stepped up his attack on the appointment, signalling the former Liberal staffer will be dumped if Labor is elected.

In a stinging rebuke of the government, a clearly livid Mr Bowen savaged the promotion as "simply wrong", describing Mr Gaetjens as a "long-term, very senior partisan player," who had served as chief of staff to Mr Morrison and before that, to then treasurer, Peter Costello.

"The Charter of Budget Honesty requires the secretary of the Treasury to sign off the pre-election fiscal outlook, which is meant to be a document thoroughly above partisan politics," Mr Bowen said.

"But the man signing it off will now be someone who a few weeks ago was the Treasurer's chief political adviser - the chief advisor to the chief spear thrower at Labor’s policies will also now be in charge of compiling the incoming government brief on these policies."