Canberra Hospital's sliding performance shows no signs of abating, with the latest government figures painting a bleak picture of the emergency department.
Just 20 per cent, or one in five, urgent patients were treated on time in the first half of 2019-20, Canberra Health Services' latest performance report shows.
The figures come as Chief Minister Andrew Barr took aim at NSW in an economic forum for under investing in health in the south-east of the state because so many of its residents use Canberra Hospital.
The government has blamed the poor figures on an increase in overall patients and the complexity of their cases.
When all five urgency categories were combined, just 38 per cent of patients at Canberra Hospital were treated on time in the first half of 2019-20. That was 32 per cent below its target.
The hospital only met its only target for resuscitation patients (category one) and non-urgent patients (category five).
In a keynote address at a Ceda economic forum last week, Mr Barr said NSW had underinvested in health infrastructure and acute health care in south eastern NSW because of the presence of Canberra Hospital in the ACT.
"At least a quarter of all patients that come through the ACT health system are NSW residents and they tend to be residents who are the sickest ... because those needs can't be met at any of their regional hospitals south of Wollongong," he said.
"We still don't have a great system for accounting for the costs of that healthcare delivery.
"That is a pressing challenge."
Health Minister Rachel Stephen-Smith said the increase in NSW patients was having an impact on wait times and the need to invest in new infrastructure.
Waiting times continue to be a challenge for our health system.Health Minister Rachel Stephen-Smith
"We are currently engaged in very productive conversations with NSW to renew our bilateral agreement," she said.
"These conversations are focused on achieving the best possible outcomes for patients in the ACT and southern NSW by building a more integrated health system across the ACT and NSW."
Ms Stephen-Smith said she was confident the hospital's performance would improve in the next few months.
She said the supplementary funding in the 2019-20 budget would help the hospital meet significant increased demand.
"Waiting times continue to be a challenge for our health system," Ms Stephen-Smith said.
"We know there is more work to be done to ensure that we are meeting the expectations of Canberrans in regard to accessing timely healthcare."
Opposition health spokeswoman Vicki Dunne said Canberra used to have one of the best performing emergency departments in the country, but now had the worst performing yet most expensive.
"Labor's priorities are perversely wrong," she said.
"The tireless and dedicated efforts of our hospital staff are coming to nothing because this tired government has not built the health service that this city needs.
"Canberra cannot afford four more years of a health system in crisis."