A long-secret inquiry into the cultural and command failures of Australian special forces operators during the war in Afghanistan has found that an "abandonment of curiosity" within the Australian Defence Force's leadership and an "inversion of authority" within units helped create a culture that allowed alleged war crimes to occur.

The inquiry found deep, systemic cultural problems were rife in the ADF's Special Air Services regiment (SAS), and that the lack of intervention to correct them indicated "an absence of effective leadership at various levels".

The inquiry was commissioned in the wake of the release of the Inspector-General of the ADF's Afghanistan Inquiry in 2020, which found "credible evidence" of dozens of unlawful killings.

It sought to investigate the culture within the special forces units deployed to Afghanistan and any causal link to the alleged killings and other wrongdoing, as well as possible indicators that more senior commanders should have picked up on.

The inquiry report was handed to the former Chief of the Defence Force, Mark Binskin, in 2022, but the executive summary was only published online recently.

The full report will not be made public, as it contains sensitive evidence from the original Afghanistan Inquiry.

The Afghanistan Inquiry has been criticised by some for its finding that responsibility for alleged war crimes sat almost entirely at relatively low ranks, amid a sense that more senior ADF officers should have carried more responsibility for the actions of soldiers under their command.

This additional inquiry found an "extreme limitation" in the flow of information from SAS units to higher levels of command at the time in question, which limited what those higher ranks knew.

But it sharply criticised the ADF's higher headquarters for not taking more of an interest in some of what it considers to be clearly alarming information that was crossing its desk, like the growing number of people being killed during operations.

"There was tangible data available for higher headquarters through trends in growing numbers of Enemy Killed in Action," it found.

"This included growth and spikes in these statistics over time, as well as features such as a lack of wounded insurgents [only deaths] and the lack of ADF casualties. By historical standards, elements of this data presented as most unusual.

"Some commanders were alert to this data and rumours that accompanied it while others were not, which may suggest an abandonment of curiosity."

It suggested that the rumours circulating about the actions of the SAS in Afghanistan surely warranted investigation at the time.

"It is extraordinary that no effective action was taken given the gravity of the matters the subject of rumours," it found.

"The issues should have been escalated and effective action taken to investigate the matters or, at the least, look behind them."

Former SAS Captain turned Liberal MP Andrew Hastie said he welcomed the release of the report because he believed in "transparency".

"I lived a lot of what I read in that report," he told Radio National Breakfast.

"There's almost 50 findings and a lot of it rings very true to me as a junior officer at the time.

"[The report] confirms there was unlawful conduct, that's not in dispute, but rather than focusing on individuals, it spreads responsibility throughout the chain of command."

'Arrogant', 'bikie gang' culture

The inquiry reserved some of its harshest criticism for the culture that developed within the SAS during the period.

It found a pervasive belief among some SAS operators that they were "exceptional" and, as a result, "ordinary norms and standards no longer apply".

But it places some of the blame on both the government and Special Operations Command for fostering the belief that the SAS was "superior" rather than "specialist", and it criticises the over-deployment of special forces more broadly.

It found a "tendency to arrogance" within the SAS, an "unhealthy imitation" of US special forces units and a belief among some that they were "untouchable".

It also found that operational decision-making was being influenced by "a desire to secure awards and the recognition and acclaim that comes with acts of valour", including "seeking out situations where significant contacts with insurgents was likely, or taking excessive risks for personal gain rather than mission effectiveness".

The inquiry found that the chain of command during the time was effectively inverted, with junior officers "effectively subservient" to non-commissioned officers who would ordinarily be under their command.

It found some junior officers prioritised "mateship" over "leadership", and criticised senior officers for knowingly allowing alcohol to be consumed.

"The creation of a dedicated drinking establishment within [special forces base] Camp Russell, particularly in an Islamic country, when there were clear orders that alcohol was not to be consumed, is striking," it found.

And it found when junior officers did try and challenge that structure, they would find networks of non-commissioned officers undermining them by effectively backgrounding against them.

It described the SAS as extremely homogeneous with a largely closed culture, "described by some as akin to a 'bikie gang'" with a "general intolerance of people who were not considered to be 'like us'".

But it noted that efforts toward cultural reform within the SAS were underway as the inquiry completed its work, and commended that attempt at change.

The findings of the initial Afghanistan inquiry led to the establishment of the Office of the Special Investigator, which investigated alleged war crimes.

Former SAS Corporal and Victoria Cross recipient Ben-Roberts Smith was arrested and charged with war crimes earlier this year, which he intends to contest.

Another former SAS trooper, Oliver Schulz, is also before the courts on war crimes charges, which he is contesting.