Home affairs departmental officials were left scrambling on how to answer a question about a “strategic review” outlined in the government’s own budget papers, with senior staff admitting to being unaware one had been ordered, or what became of it, documents released under freedom of information laws reveal.

The review into Peter Dutton’s department was ordered just five months into the creation of the super-portfolio to identify “integrating capabilities, reducing duplication and maximising efficiencies”, with the then treasurer Scott Morrison setting aside $7m for the project in the 2018 budget papers.

In response to media inquiries about the state of the review, a departmental spokeswoman said it had been completed, but the report would not be released.

The Senate then passed a motion demanding the report be tabled in parliament, only for Dutton to respond no such report existed, despite a $5m spend on consultants and contractors.

A response to a freedom of information request from the Guardian into how the department had come to claim it had not released a report Dutton later claimed didn’t exist reveals the confusion within the department about what the strategic review listed in the budget papers was referring to.

The assistant secretary of enterprise governance and risk division responded “this review is not me and I am not aware of it”, when approached for information, despite the relevant budget paper having been included, with the inquiry bouncing around, as officials tried to undercover what the budget paper was referring to.

Eventually it was decided that the $7m review in question was related to a portfolio capability roadmap completed by the department in late 2018.

First assistant secretary in the capability, planning and development division of the department, Angus Kirkwood, gave approval on 5 July for the response that included that this roadmap “has not been publicly released”.

“A Home Affairs Portfolio Capability Roadmap was completed and provided to the Minister for Home Affairs in late 2018. The report has not been publicly released,” the original statement read.

But mentions of the roadmap were removed from the statement before it was provided to the Guardian. It was revised to: “A Home Affairs Portfolio Review was completed and the report has not been publicly released.”

Emails show that the response was also sent to the office of the home affairs minister, Peter Dutton, “for noting”.

The department conceded there would be more questions from journalists following its response, instructing media staff to say “we have nothing further to add” when the inevitable followup queries came. Events played out as predicted.

The response was eventually provided to the Guardian on 8 July.

It wasn’t until the end of July, when Labor sought the tabling of the report in the Senate after seeing the Guardian’s story, that the department revised this statement again to claim there was no such report, and instead the strategic review comprised of “a number of packages of work undertaken”. “This did not form one review that can be released.”

Once Labor’s Kristina Keneally passed the motion demanding the report the department referred to be tabled, Dutton’s office became involved in explaining why the report did not exist, with the department admitting it had “incorrectly” provided a response the strategic review had been finalised.

Keneally said the scramble for answers within the department shone some light on why home affairs staff reported having the lowest morale within the public service.

“Let’s get this straight – the Department of Home Affairs couldn’t even answer three basic questions about their own strategic review: Was it done? What did it find? Will it be released publicly?,” she said after seeing the FOI response.

“If this is what taxpayers get for $7m of strategy advice under Peter Dutton, heaven help us. It’s no surprise that a recent survey showed that the Department of Home Affairs ranks dead last among public service agencies for morale, and that one in every three people working in home affairs wants to leave.”

Home affairs officials will face budget estimates on Monday.