Mr Barnes says the Commonwealth "resisted the provision of further information", meaning he could not determine if the "traditional roles of domestic police forces and the ADF [Australian Defence Force] in Australia ought to be reconsidered" .

The Commonwealth rejected Mr Barnes' request on the grounds that ADF personnel were only present at the December 2014 siege in a liaison role, that policing was not comparable to potential actions by the ADF, and that providing the information could "expose ADF methodologies."

He makes no explicit criticism of the Commonwealth's position, but says the refusal to share more information meant the inquest could not "comprehensively examine the ADF issues".

"In particular, it [the inquest] was not able to thoroughly consider the role the ADF might have played if called out, the ADF's capabilities generally, and whether or how those capabilities differ from those of the NSW PF [ state police force]", he says.

The revelations, buried in detail towards the back of Mr Barnes' wide-ranging 500-page report on the cafe siege, are significant.

While ministers from the Prime Minister down are now talking about examining more seamless co-operation between the armed forces and police in terrorist crises, it appears that thinking was not at the forefront of the Defence hierarchy's mind in late 2014, when gunman Man Haron Monis took 18 customers and staff hostage inside the chocolate cafe.

Mr Barnes says the Commonwealth did comply with a request to provide statements from 11 Australian Defence Force officers "who performed duties relating to the siege".

But he said the statements gave just a brief overview of liaison and observation activities on the night and "did not provide a description of the ADF's capabilities or the way it would have approached the siege if called out."

When the inquest team sought to identify the commander of the 11 ADF members who sat alongside police at various times during the siege, the Commonwealth "did not accede to that request", he says.

"All told, comprehensive evidence regarding potential intervention by the ADF is not available", he adds.

The federal government has two specialist army assault teams - Tactical Assault Group (or TAG) East, and TAG West - based in Sydney's Holdsworthy, and Perth respectively, to deploy rapidly in domestic counter-terrorism operations.

But Mr Barnes says TAG East could only have been deployed under current "defence call-out" provisions if NSW police had decided the Lindt siege was beyond their capabilities. That did not happen, although TAG East did construct a mock-up of the Lindt cafe as part of its preparedness.

The Coroner says there are "sound reasons" why police should be principal managers of domestic terrorism incidents but that "it is beyond question that with the rise of global terrorism and Islamic jihadist movements, the domestic security environment has shifted significantly in recent years."

He notes the Commonwealth has now started reviewing the support defence might provide in future terrorism scenarios.