Under-fire telco Optus has announced an independent inquiry into an outage that left people unable to access triple-zero services and has been linked to four deaths.

Kerry Schott will lead the external review, which will press for the causes of the outage and examine the operational management of triple-zero calls on the Optus network.

It will also look at Optus’ response to the incident and whether it adhered to policies and legal requirements.

Schott is a non-executive director of AGL Energy and chair of the Carbon Market Institute and the federal government’s Competition Review Panel. She is also a former Sydney Water boss.

Her appointment came as embattled Optus chief executive Stephen Rue blamed the outage on human error when he fronted the media on Wednesday.

Rue brushed off concerns parent Singtel had cut spending to Australia’s second largest telco.

“Standard processes were not followed,” he said.

“That’s not an investment issue, that’s people not following process. That is a result of human error.”

Singtel Group defied the demands to sack Rue, a former NBN Co boss brought in to right the ship after scandals.

“Our hearts go out to the families and friends of those who have passed away and we know that Optus will get to the bottom of this matter,” Singtel Group chief executive Yuen Kuan Moon said in a statement.

“We will continue to fully support the Optus board and management team as they work through this incident and accelerate the changes needed.”

Board chairman John Arthur also appeared to stand by Rue.

“The Optus board is working with CEO Stephen Rue and his team to ensure we develop a full understanding of what went wrong and why, and what we need to do to prevent any repetition,” he said in a statement.

Asked about calls for his resignation, Rue said the situation was not about him.

“What we have here is lives have been lost, a failure of triple zero, processes in call centres but also in network, not being followed,” he said.

“There are no words that can express how sorry I am about the very sad loss of the lives of four people who could not reach emergency services in their time of need.”

The Federal Court on Wednesday added to the Optus pile-on after approving a $100 million penalty for the company over “appalling and predatory” conduct in its sales practices.

Optus admitted its sales staff acted unconscionably when selling phones and contracts to more than 400 people at 16 stores nationwide between 2019 and 2023, including vulnerable customers such as Indigenous and intellectually disabled people.

“Senior management abrogated their management responsibilities and, consequently, Optus abrogated any semblance of responsible corporate behaviour,” Judge Patrick O’Sullivan said.

–AAP