Communications Minister Michelle Rowland said connectivity was “absolutely essential” for consumers and businesses, while announcing the federal government’s investigation.

“While we welcome that Optus services were restored over the course of the day, it is critical the government conducts a process to identify lessons to be learned from yesterday’s outage,” she said on Thursday.

The minister said she would task her department with developing the terms of reference for a post-incident review.

The Australian Communications and Media Authority has independently started to investigate Optus’ compliance with the rules on emergency calls, while the telecommunications watchdog urged small businesses to get in contact with Optus to discuss options for compensation.

“What we would encourage you to do is contact Optus and … help them understand what the impact was on them and their earnings,” Telecommunications Industry Ombudsman Cynthia Gebert said.

“That’s the sort of thing that we think you need to tell Optus so they get a sense of what sort of compensation might be the right thing to do for your circumstances.”

Gebert said the scale of the outage was unacceptable, as it impacted emergency services and hospitals in addition to small businesses and transport services.

Financial Services Minister Stephen Jones slammed Optus’ response as “absolutely subpar”.

“You’d have thought coming off the back of the previous data breach where they were facing similar calls from customers to explain exactly what was going on, this simply wasn’t good enough,” he said.

Businesses are counting the costs after the nationwide outage ground trading to a halt.

More than 10 million customers and businesses were thrown into disarray from about 4am, with customers prevented from connecting to the internet or making or receiving calls.

It took more than 12 hours to restore services.

The shutdown hit SA government agencies including SA Health, with hospital switchboards offline and “substantial inconvenience” caused, although Premier Peter Malinauskas said there was no clinical affect on patients.

The Premier criticised Optus for its lack of communications during the telecommunications crisis.

“We are disappointed with Optus, they’ve let their customers down across the state, including the government,” he said on Wednesday.

“Optus need to respond swiftly, communicate effectively with everybody about exactly what is going on here. Telecommunications now is central to the functioning of the Australian economy, and it has a big impact on services across governments.

“And if Optus wants to see government as a customer then they need to be able to be a reliable service.”

Optus chief executive Kelly Bayer Rosmarin said the cause behind the blackout was a “technical explanation”.

“There is no soundbite that is going to do it justice, so we want to really bottom out the root cause and when we have that very clear and in a digestible form, we will be forthcoming,” she told the Australian Financial Review.

Bayer Rosmarin said she had “no idea” how long it would take to do a “full and thorough root cause analysis”.

The outage was not “something unusual in the grand scheme of things when you’re operating a critical infrastructure like we are,” she added.

The Greens are pushing for an inquiry in the Senate.

Businesses had been dealt multiple blows, a day after the Reserve Bank increased interest rates, National Retail Association director Rob Godwin said.

“This is costing businesses thousands of dollars in sales that they are now in dire need of given yesterday’s rate hike,” he said.

Victorian Premier Jacinta Allan said the government would review the state’s contracts with Optus as well as the telco’s response.”

Whether you’re a small business operator here in Victoria, someone trying to get to work on the train … it was a really, really disappointing incident,” she said.

Optus is one of 23 telecommunication providers contracted by the Victorian government.

Almost 10 million Optus customers had their personal information stolen during a massive data breach last year.

The company believes a network fault was behind Wednesday’s outage.

People weren’t able to call triple zero on landline devices, although it was still possible to do so on a mobile phone.

-with AAP

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