The Department for Work and Pensions (DWP) has failed to reduce the mistakes made in processing benefits, partly because of poor IT systems, a report from the National Audit Office (NAO) has found.
The DWP has an annual IT budget of about £1bn. In 2009-10, the DWP overpaid its customers by an estimated £1.1bn and made underpayments of £500m.
This is in part due to the department's 140 core processing systems, many of which are relatively old and not well-linked to others, said the NAO report.
Small changes to systems to combat human error can be problematic, the NAO found. "For example, we asked the department to consider the feasibility of introducing a double-keying requirement. [But the] changes required would be complex and the feasibility work to provide even a rough estimate of costs would be significant," it said.
"The department continues to work on system 'fixes' but until it is able to develop a solution to enable integration of its processing systems, the overall impact on administrative errors is likely to be limited," the report added.
Auditor general and head of the NAO Amyas Morse said it was "frustrating" that administrative errors had not been discernibly reduced since since 2007.
"Progress will depend on developing a better understanding of the costs and benefits of different interventions, so that they can be targeted more effectively and are able to achieve a significant reduction in the cost of administrative error," he said.
At Jobcentre Plus, the advice line receives around 5,000 calls a month, 35% of which are about IT issues.