Hospital management was concerned about the "unusual" incident, which was described as the "tip of the iceberg" by the Opposition.

There would be a coronial inquest into the man's death, as well as an internal investigation conducted by doctors and nurses.

Deputy Opposition Leader Jacqui Burke said the Government must take responsibility for the tragic case and heed health workers' warnings about problems in the system.

"The death of Allan Osterberg, who was found to have no pulse after having been slumped in his seat in the waiting room for four hours, is an indictment of Labor's failure of management," Mrs Burke said.

"It is an indictment of a system that is overly bureaucratic, unaccountable and resistant to improvement."

Mr Corbell defended the system.

"The emergency department sees thousands and thousands of people every week," he said.

"This is a very busy tertiary treatment emergency department and in any large system, it is not fail-safe.

"But because, what appears to have been, a mistake or a series of mistakes have been made is not indicative of the safety of the system overall. The safety and the quality of care overall is of a very high standard."

The controversy centres on the death of Mr Osterberg who arrived by ambulance at Canberra Hospital's emergency department about 10.30pm on Friday.

The man was experiencing gastro-intestinal problems but did not display symptoms associated with a heart attack, according to Mr Corbell.

ACT Health chief executive Mark Cormack said Mr Osterberg was triaged as a Category 3 case a patient with an urgent medical problem and treatment should start within 30 minutes. Emergency department staff did a "number of standard checks" on Mr Osterberg before he was moved into the waiting room which was "not uncommon" for Category 3 patients.

"He was noticed to be slumped in his chair around about 3am and was immediately bought in for resuscitation ... and subsequent to that was taken up into the ICU and he died in the afternoon of Saturday," Mr Cormack said.

"It's obviously a concern that a person would apparently and I stress it's apparently suffer a cardiac arrest in the waiting area."

Police would interview staff and review records as they prepared a report for the coroner. As the same time, hospital doctors and nurses would conduct a "clinical review" of the case to pinpoint any systemic problems.

"We're concerned that this thing has happened and we'll be doing everything we can to identify the system issues that may have been at play," Mr Cormack said.

"As we do with other adverse incidents, we will put in place strategies, changes and programs in the service to reduce the risk of that happening again."

Mr Corbell rejected pleas for a government inquiry into the incident, saying that the coronial inquest and clinical review would be sufficient.

He expected the clinical review committee to produce a report in less than a month. Mr Corbell said the Government had made improvements to the hospital system, including opening two more operating theatres and providing funding for 147 more beds.

Almost 100,000 patients were treated last year at ACT public hospital emergency departments.

"Without strong levels of primary care available in our community and having equitable access to ... your local GP, we are going to ... continue to face enormous growth in demand for emergency department services," he said.

The ACT had the lowest bulk-billing rate in the country and a chronic shortage of GPs.