In Senate estimates on Monday, Home Affairs Secretary Michael Pezzullo revealed the leaders of the agencies covered by the Home Affairs portfolio, including Australian Border Force commissioner Michael Outram, AUSTRAC chief executive Nicole Rose, Australian Criminal Intelligence Commission chief executive Michael Phelan and ASIO director general Mike Burgess, had begun a cross-portfolio board.

"More needs to be done to fully realise significant future opportunities, especially in relation to improved strategic and financial planning, capability development and acquisition, technology, collaboration, intelligence and data sharing, consolidated business services and where appropriate cross agency workforce mobility," Mr Pezzullo told the committee.

"Our work as a board will be greatly assisted by the outcomes of the strategic review of the portfolio which was funded in the 2018-19 budget," Mr Pezzullo said.

"Of the $7 million allocated for this purpose in the budget, less than $5 million was expended on the development of financial models and planning tools, and a capability inventory, which will support our work to identify opportunities for increased efficiencies, to better understand our costs, and to better manage our assets, including by way of giving high quality advice on investment options and choices."

Earlier this year, the department responded to media requests for the strategic review by saying a document existed but wouldn't be released. Later after the Senate passed a motion demanding it be tabled, Home Affairs minister Peter Dutton said the document didn't exist.

Instead the $5 million already spent hadn't produced a "single consolidated report".

A report in The Guardian on Monday revealed chaos within the department over the review, with Home Affairs officials unsure what the document referred to in the budget papers actually was when asked for it by journalists.

At estimates on Monday, Home Affairs officials attempted to explain the confusion around the report and its existence.

Senators were told the strategic review came in under budget, and produced a number of documents, but no single report.

Mr Pezzullo said there was no secrecy about a review that was announced as a budget measure, and that the emails published under Freedom of Information were "offices diligently transacting amongst themselves".

Mr Pezzullo said officials were trying to work out whether a single document existed or if there was more than one.

"The strategic review was complex," first assistant secretary Angus Kirkwood said, explaining that many different areas of the department had worked on the review, contributing to confusion around .

Mr Pezzullo said the strategic review "informed a number of documents, some of which are the subject of ongoing consideration".