In the wake of the 2003 bushfires, the ACT government resolved to build a new co-located headquarters for the Emergency Services Agency.

It put extensive work into a potential site in Hume, near where the ACT's jail now sits, conducting a feasibility study and consulting widely.

That site would have allowed it to construct buildings that met its exact requirements.

Newly-released classified documents from 2005 reveal that cabinet had agreed on the Hume site, but were asked to reconsider when the ESA put forward a proposal to rent existing buildings from the Capital Airport Group at Fairbairn instead.

The airport proposal was put forward on the recommendation of former ESA Commissioner Peter Dunn.

It was argued that the buildings would be available quickly, and the option would better suit the operational needs of the agency.

But it also meant the ESA would be renting buildings to house critical infrastructure, meaning they lost control over their design and suitability.

The move would later turn out to be plagued by problems, was costly and hit by significant delays.

In 2007, an auditor-general's report found total project cost blew out from $11.6 million to $75.3 million, and the process was "not supported by any detailed analysis of operational requirements or financial implications".

The auditor-general found the decision appeared to be "based on the availability of buildings rather than on identifying the needs of the ESA".

"The doors of the building are too narrow for large vehicles, the ceiling is too low, the concrete slab is too weak to support large jacks and large vehicles and it does not contain a pit for mechanics," the report found.

Freedom of information documents released in 2011 showed the government had been repeatedly warned that the Fairbairn headquarters was insufficiently planned and unnecessarily costly.

Newly-released cabinet documents show that Treasury, while supportive of the ESA's Fairbairn proposal generally, raised several concerns about the option.

In 2005, while commenting on the ESA's final submission to cabinet, they warned the government would not get value for money unless they went out to a competitive tender process.

"Treasury notes that under normal circumstances a competitive tender should be conducted to ensure that the Territory achieves the best value for money available in the market," then Budget Management Branch acting director Floyd Kennedy wrote.

"The process adopted for this proposal has not allowed for this to occur," he said.

"As such, Treasury recommends that the submission be amended to advise cabinet of the risks associated with proceeding with the Fairbairn option without market testing through a competitive procurement process."

Earlier, Treasury officials had strongly criticised a draft cabinet submission put forward by the ESA on the proposal.

They warned that the analysis of the implications of leasing existing buildings was "basic at best", and failed to look at the financial and operational factors specific to critical ESA infrastructure.

"The analysis of the implications of leasing versus ownership is basic at best ... It is not a detailed financial and operational analysis of the specific factors relevant to ESA critical infrastructure," Treasury officials wrote.

"The submission does not adequately explain how the longer term leasing arrangements will be managed to ensure a continuing commercially competitive arrangement.

"The option of the government owning its own site for essential emergency service facilities has the advantage that the government is not subject to later high rents because there are limited or no alternatives."

A spokeswoman for Emergency Services Minister Simon Corbell, who was not in the portfolio at the time, said the Fairbairn proposal had been put forward by former commissioner Dunn, and his proposal was accepted by cabinet.

"Subsequent inadequacies in the governance of the headquarters project was a major reason for the incorporation of the ESA within the [Justice and Community Safety] portfolio in 2006," a spokeswoman said.