Chief Coroner Lorraine Walker's investigation will focus on the 45 minutes it took for the helicopter crew to alert the ACT Emergency Service Agency to the fire's location after their aircraft's landing light accidentally ignited the blaze.

In a statement announcing the coronial inquiry on Wednesday, Ms Walker said it was in the public interest that all "relevant matters concerning the cause and origin of the fire - and the actions taken to respond to it - are fully considered".

Emergency Services Minister Mick Gentleman and Emergency Services Agency commissioner Georgeina Whelan both said the ACT government and its agencies would participate in the inquiry, but improvements made since the blaze meant Canberrans were better protected.

"Noting that the Coroner's scope of inquiry appears to be focused on the actions of Defence, Canberrans should be assured that our emergency services are well equipped to spot fires quickly regardless of the source of ignition," Mr Gentleman said.

"Our fire towers spotted smoke from the Orroral Valley fire within approximately 19 minutes of ignition and our crews were tasked with responding immediately."

READ MORE ORRORAL VALLEY FIRE

The fire burned through 80 per cent of Namadgi National Park after it ignited about 1.30pm on January 27. No homes were destroyed in the ACT, however about a dozen were lost after it skipped the border into NSW.

The ACT coroner cannot investigate what happened in the NSW.

"The Orroral Valley fire burned throughout the territory for one month, and is a fire of public significance," Ms Walker said in the statement.

"It is appropriate in the circumstances that I hold an inquiry into this significant fire."

Defence has repeatedly defended its handling of the January 27 incident, insisting its priority at the time was to return the crew to safety after their MRH-90 Taipan was damaged.

The helicopter had been sent to Namadgi to find locations where it would be safe to drop off and collect remote firefighting teams.

Ms Whelan has repeatedly refused to criticise the crew's action. She has consistently maintained the delay wouldn't have made a difference to the agency's response to the fast-moving fire, as it had deployed crews within 19 minutes of the fire's ignition after smoke was spotted from Mount Tennent tower.

Ms Whelan said in a statement on Wednesday her agency had participated in several inquiries, hearings and reviews into the 2019-20 bushfire season.

"As the subsequent reports from these processes highlight, we have learned valuable lessons from these reviews, which challenged conventional emergency management assumptions and tactics."

Ms Whelan said improvements had been made across the agency, including improvements to collective training, preparedness, personnel, planning and incident management strategies.

"This extensive work means Canberrans will be even better protected and informed during natural disasters into the future. Our thoughts continue to be with those who were affected by the ACT fires, especially those who lost homes in NSW," she said.

Defence has been contacted for comment.

Earlier this year ACT Chief Minister Andrew Barr even likened media scrutiny of Defence's role to a "witch hunt", insisting that an "endless circular blame game" would achieve nothing.

Mr Barr on Wednesday did not say whether he thought the inquiry was necessary but said in a statement the ACT government would provide assistance to the coroner and examine relevant findings.

"The ACT government reviewed the 2019-20 bushfire season to ensure any lessons would bolster future emergency responses," Mr Barr said.

"This included our engagement in the Royal Commission into Natural Disaster Arrangements, the ACT Standing Committee on Justice and Community Safety, Review of Whole of ACT Government Coordination and Response during the 2019-20 Bushfire Season, and the ACT Emergency Services Agency Operational Review of the Bushfire Season 2019/20."

Scrutiny of the incident escalated in January, after Defence published images of the nascent blaze which had been captured by the helicopter crew.

The Canberra Times last year reported that at least one senior figure working inside the agency's incident management team had questioned why the military helicopter was sent to Namadgi on January 27.

"Was this a case of using a resource simply because it was there to showcase to the public how the ESA was effectively utilising the military resources it had engaged?" the senior official said in a confidential submission to the ACT Legislative Assembly's inquiry into the probe.

More to come.

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