“We apologise for the inconvenience, our tech teams are looking into this with urgency.”
Westpac One was unavailable for both browser and app (iOS and Android) users.
However, the bank said card services and ATMs were unaffected and scheduled payments were working as normal.
The technical glitch left customers frustrated that they could not complete online transactions. At least one customer was unable to pay for petrol to get to work.
“A text would have been great so people aren’t stressing. I was literally trying to do a transfer but couldn’t get in,” one person said on Facebook.
Another said their daughter was trying to top up a Hop card but couldn’t.
“This happens at least once a week, I have bills to pay and can’t access my account!!!!!,” another said.
Others might be a little late for work: “Sucks Much! Can’t even transfer funds to Gas my Car this morning.”
A peak of 581 people had reported an outage on Downdetector.
Westpac had issues with its online banking services on March 18, March 20 and April 9, according to the incidents history on its website.