Commonwealth Bank's claim to being Australia's most reliable online banking provider is in tatters as its internet and mobile banking platforms suffer one of their most prolonged outages on record. The flagship online systems, NetBank and CommBank App, began malfunctioning at around 6.00am on Monday and customers continued to report problems on social media late into the night. As Banking Day went to press early on Tuesday morning, the bank had not updated its status on Twitter since just before 8pm the evening before - saying it was "continuing to work on this issue". The platform outages were compounded by a meltdown in the bank's electronic link to the Visa processing system that caused all transactions initiated by Visa cardholders on CBA-owned eftpos terminals to be rejected. A bank spokesman attributed the outages to problems at one of CBA's main data centres that reduced the processing capacity of the online services. "There was an issue in one of our two data centres, which led to all NetBank and CommBank app traffic routed through our other data centre," the spokesman said. "This reduced capacity has caused some users to experience issues logging in and making payments or transfers." Several observant NetBank users noted that they began experiencing problems using their online accounts on Saturday after the bank's IT team completed regular maintenance on the site. The technology meltdown disrupted payments transactions across the country, with retailers reporting thousands of customers abandoning goods at checkout counters. Retail and business customers continued to report problems accessing the bank's services on Monday night. Service outages have become a regular occurrence for CBA this year, with customers reporting 26 service disruptions since 1 January according to the online research site - Aussie Outages (www.aussieoutages.com). While that is nine fewer than ANZ - the industry's most frequent offender - the duration of CBA outages appear to be greater than disruptions reported for other banks. CBA service disruptions have persisted on average for around four hours this year compared to three hours for ANZ. So far this year there have been more than 100 disruptions of online banking services operated by the four major banks. One of CBA's biggest challenges on Monday was its bungled communications with customers on social media. The bank appeared to exacerbate the public backlash from customers by prematurely announcing at 12.23 in the afternoon on Twitter that its online services had been restored. "Transfers and payments are now working in NetBank and the CommBank app," CBA told customers on Twitter early in the afternoon. "As we restore services some users may experience log-on taking a little longer than normal." However, the bank conceded more than seven hours later that not all customers had access to online services and that IT staff had still not fixed the problems.