Treasurer says Aussies shouldn't lose faith in triple-zero network after Optus' fresh outage

Australians should not lose faith in the triple-zero system despite Optus' "shocking failure" of three outages in two years, Treasurer Jim Chalmers has said.

About 4500 Optus customers were affected by an issue involving a mobile phone tower in NSW's Dapto region between 3am and 12.20pm yesterday.

It affected calls, including nine to triple zero.

READ MORE: Daughters hit rock bottom after botched case against dad's murderer

Optus said all people who attempted to contact triple zero were "OK", with several of them being accidental or test calls.

Services have since been restored.

The telco is under fire over a triple-zero outage that affected more than 600 calls and was linked to three deaths on September 18.

Chalmers told the media today that it was a "shocking failure" that "can't happen again", but said Australians should not lose faith in the triple-zero system.

"The government is getting to the bottom of it," he said.

"(Australian Communications and Media Authority) is the most appropriate body to conduct that very thorough investigation.

"Optus has clearly failed here on a number of fronts. Our focus as a government is getting to the bottom of what went wrong."

Premier Chris Minns also slammed Optus' latest outage as "clearly unacceptable".

"New South Wales deserves full and transparent information from Optus about what went wrong yesterday, including when emergency services and the telco authority were notified," he said.

"Our emergency services have worked tirelessly to check on the welfare of those affected by this outage, and that work will continue today."

READ MORE: Two arrested after machete death as tributes flow for 'loving' teen

Minns added that while there were no reports of adverse patient outcomes from this incident, it highlighted just how critical reliable communications are.

"Which is why we welcome the federal government and ACMA's investigations into Optus," he said.

Optus chief executive Stephen Rue blamed the September 18 outage on human error, saying a firewall upgrade had been botched.

"Preliminary investigations have determined that on the first night of the upgrade, the steps taken on past successful upgrades of a similar nature were not followed," he said last week.

"On this occasion of the upgrade of 18 September, the first step in the process was not followed."

Communications Minister Anika Wells has warned of "consequences" for the telco giant, but no specific penalties have yet been handed down.

An Australian Communications and Media Authority investigation is ongoing.

Optus has previously received a $12 million fine for a triple-zero outage that affected more than 2100 customers in 2023.

DOWNLOAD THE 9NEWS APP: Stay across all the latest in breaking news, sport, politics and the weather via our news app and get notifications sent straight to your smartphone. Available on the Apple App Store and Google Play.