The boss of Australian telecommunications company Optus has resigned after a nationwide outage affected millions.

CEO Kelly Bayer Rosmarin quit after a senate grilling last week.

She'll be replaced by the Chief Financial Officer.

A major cyber attack last year - also under her tenure - compromised personal documents of two million customers.

Australia correspondent Oliver Peterson says her handling of the outage was criticised.

"She was very reluctant to get onto the front foot, didn't say much- finally came in kicking and screaming to actually reveal what had happened."

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