Telstra has been hit with a $3 million fine for failing to comply with emergency call rules during a triple-0 network disruption in March.

It comes after Optus was ordered to pay $12 million in penalties when thousands of its customers were unable to call triple-0 during last year's unprecedented network outage.

Telstra is Australia's national operator of the Triple Zero service, meaning it is required to comply with obligations in relation to the handling and transfer of calls made to emergency service numbers.

An investigation by the Australian Communications and Media Authority (ACMA) found Telstra made 473 breaches of the rules during a disruption on March 1.

The ACMA said Telstra's Triple Zero call centre was "hampered in transferring calls to emergency services for 90 minutes".

The investigation found Telstra initiated a contingency process to transfer calls received during the disruption by using a list of backup phone numbers.

But 127 calls were not transferred to emergency services due to several of the phone numbers on the list being incorrect.

Telstra managed those calls by providing the callers' details to the relevant emergency service organisations through email messages and phone calls.

The authority said Telstra could also not provide the caller's digital location information to the emergency service organisations due to the disruption, despite successfully transferring the remaining 346 calls. 

ACMA member and consumer lead Samantha Yorke said Telstra neglecting to update its backup phone data was a concern. 

"Telstra, as the emergency call provider, is at the centre of this critical public safety service," she said. 

"As such, it must have fail-safe systems and processes in place at all times. 

"In this circumstance, its systems and contingency plans failed people in real need."

Ms O'Loughlin acknowledged Telstra's historically strong record of compliance in its role as the national Triple Zero operator.

"Telstra has been open and apologetic about the outage, communicated effectively to the public and took a variety of immediate actions when problems were identified," she said. 

"These actions go a long way to restoring the community's trust in this critical service."

The ACMA also noted Telstra's actions to rectify its processes following the incident, including updating its backup phone number list and appointing an independent consultant to conduct an incident review.