Tesco Bank has confirmed its online services are now fully operational after some customers were unable to log into their savings accounts.
The bank's customers faced difficulties logging into accounts at the end of June 2011 following a migration glitch. Tesco Bank said all savings customers should now be able to access online accounts.
"Our online service is now fully operational. We apologise to any of our savings customers who continue to have difficulties registering online," said Tesco Bank.
Tesco Bank added it is still receiving high volumes of calls but waiting times were beginning to reduce.
Tesco Bank systems crashed as it migrated savings and loans accounts from in-house systems at its former partner Royal Bank of Scotland (RBS).
After an initial glitch, the company said the process was complete and its online banking system had returned to normal service. But several days later, a spokesman confirmed some Tesco Bank customers remained locked out of their accounts.
Tesco set up its own core banking system in November 2009, when it selected an off-the-shelf core banking system from Fiserv in its move to becoming a retail bank. Tesco Bank went live with the system 11 months later.
Tesco Bank's efforts to improve technology as a key driver for growth in the UK and overseas prompted an increase in Tesco's capital expenditure on banking IT last year. Capital expenditure in the UK was £1.7bn, with an additional £200m in the group's banking arm.