UK bank Abbey has acknowledged that service to customers has been disrupted as it grapples with migrating to a "state of the art" core banking system.
The bank said only a small number of customers had been affected. But staff say they are under pressure because of difficulties with the roll-out.
Linda Rolf, general secretary at the Abbey National Group Union, said, "I am aware of the system problems and we have discussed it with management. The systems are improving and will improve further."
The project, which will replace 30-year-old legacy systems, will help Santander cut IT costs by £305m following its acquisition of Abbey in 2004 for more than £8bn.
Abbey said in a statement to Computer Weekly that, "Our staff are working hard to ensure a smooth transition. In a project of this scale and complexity there will be some disruption to the service we offer while we adapt to new ways of working and serving our customers.
"While this is in no way acceptable for those customers who may be affected, we know it has impacted a small number only, and in the majority of instances it is not a system problem, but more to do with the change to the processes and the logical learning curve after a change of this magnitude."
Abbey said the project required immense effort and was exceptional in the finance industry. The project is 70% complete, with major milestones, including creating a resilient datacentre, renewing branch communication infrastructure and creating a single database, complete.
Some customers have complained about difficulties accessing services and long queues in branches as the new system is rolled out.
A handwritten sign at one branch of Abbey last week read: "Due to system problems your queuing time may be in excess of 25 minutes." It recommended alternatives such as the cheque deposit box, depositing cash or cheques in the cash point and in-branch phones for transfers and account card enquiries.
Partenon is an online banking system with what is known as straight-through processing capabilities, where every relationship a customer has with the bank is on the system, offering customers access to everything they need from one point of contact.
This is an advantage to banks in today's multi-channel banking environment and was one of the reasons Abbey's sale was approved.
Project milestones achieved
● Business continuity risk cut by new resilient datacentre infrastructure. Project involved replacing more than 18 tons of cable.
● Single database created to hold all customer data. Some 52 million customer records consolidated into 18 million to enable single customer view.
● Migration of 10 million savings accounts, four million current accounts and eight million card accounts to new software platform.