The father of one of three soldiers killed during an insider attack in Afghanistan says the incident was caused by incompetence and was preventable.

BRISBANE, Oct 27 AAP – Negligence and incompetence caused the deaths of the Australian soldiers killed during an insider attack in Afghanistan, his father says.

Lance Corporal Stjepan Milosevic, Sapper James Martin and Private Robert Poate were gunned down by a rogue Afghan National Army soldier while on a mentoring mission at an Oruzgan province patrol base in August 2012.

A coronial inquest into the deaths has raised questions about the army’s preparedness for a so-called green on blue attack, whether systemic failures in the Defence Force contributed to the soldiers’ deaths, and the independence of the army’s internal investigation.

The inquest was held at the request of the families of the three men.

Hugh Poate, the father of Pte Poate, says senior commanders betrayed the trust placed in them by soldiers on the ground.

Intelligence known further up the chain of command regarding insider attacks was not passed down, Mr Poate told ABC TV’s Four Corners.

“Those men would still be alive today in my view if the force protection measures that were implemented immediately following the incident had been in place, and should have been in place, at the time of the incident,” he said.

Mr Poate said given the port-Ramadan period and the escalation of green on blue attacks, it was only a matter of time before the Australian soldiers were hit.

“Common sense suggests that what they should have done was beefed up those force protection arrangements.”

The man responsible for the attack, named Hekmatullah, has been sentenced to death after being tracked to Pakistan and arrested in early 2013.

Hekmatullah, in an interview with the ABC, has sought forgiveness from the families of the men he killed.

He said he had carried out the murders after being angered by a film showing copies of the Koran being burnt by Americans.

“I was so angry that I carried out this action. If this abuse goes on I will do it again,” Hekmatullah said.

Mr Poate said he hoped Hekmatullah’s death sentence would be carried out.

“He showed absolutely no mercy to our boys,” Mr Poate said.

“He killed them in the prime of their lives. They had done nothing to him other than befriend him and he turned around and just killed them in premeditated, cold-blooded murder.”