Issues with Westpac's online and mobile banking systems have extended into a second day, going down this morning after coming back online last night.
Westpac customers were unable to access mobile and online banking yesterday from 10am to 7pm.
Westpac last night advised the system was back up and running and it was investigating the cause.
But online and mobile banking services went down again from around 9am this morning until 4pm this afternoon.
The bank declined to comment on the cause but said it was working on a fix.
Responding to reports of a distributed denial of service (DDoS) attack being behind the outage a bank spokesperson said there was 'absolutely no indication of malicious activity directed at Westpac'.
Westpac is preparing for the introduction of a new online and mobile banking platform, to be underpinned by Fiserv technology.
It is scheduled for release around late 2013 or early 2014. Westpac signed the deal for the system in July 2010.
The bank revealed in May it had delivered the first two of six releases for the new online platform during the first six months of 2013.
IT solution and service provider Remasys independently monitors the performance of the big four banks. Below is the company's graph of Westpac's response performance from 7am Thursday to 11am Friday.
The dark blue line refers to Westpac's Home Page. All other data refers to the online banking funtions.
Update 4pm 2/8/13: Westpac said it had restored full functionality to online and mobile banking services.
"We take systems reliability extremely seriously, are very disappointed by inconvenience to our customers and will undertake a thorough review," it said in a statement.
"Our sincerest apologies to all and thanks for your patience."