National Australia Bank's online and telephone banking services have collapsed again.
Customers were unable to access their accounts online for most of the day while telephone banking was also briefly affected in the morning.
A spokesman told The Australian newspaper that the outage was caused by a glitch with its secure log-in system and there were no security risks.
NAB took to Twitter in a bid to calm disgruntled customers and urge them to use the telephone service. Online banking was restored by the afternoon but was running slowly due to "high volume of users".
The bank spent much of December suffering from payment processing problems attributed to a "corrupted file in the processing batch" leading to thousands of complaints.