Siemens is suing e-commerce specialist Axon, which project-managed and installed the SAP systems for WHSmith as part of a move to integrate IT systems in 50 news delivery depots, for undisclosed damages.
Siemens is understood to have alleged that modifications made by Axon and WHSmith to the SAP software were responsible for the system failing to meet its performance targets.
WHSmith claimed it was forced to replace Siemens' database services with IBM pSeries 680 servers, after struggling for 18 months to implement a workable SAP solution.
Siemens had offered WHSmith a guarantee that the project would not suffer if its calculations of the amount of computing power needed to run the system proved inaccurate.
However, the project ran into difficulties within months of the work starting. The database servers were operating at 70% capacity, with only 15% of WHSmith's operations live on the system, court documents revealed.
"Users could not carry out many operations the system was designed for. The principal reason for the deterioration in performance was insufficient processing capacity on the database server," WHSmith said.
The project, which exceeded its original £15m budget by £8m, sparked a volley of complaints last year from newsagents, who claimed they were forced to spend inordinate amounts of time sorting out the system's teething problems.
Axon this week said it would vigorously defend itself against Siemens' accusations. The company plans to issue a formal defence document within the next three weeks.
Fujitsu Siemens and Siemens have issued a counter claim for £1m against WHSmith, alleging that the difficulties in the project were caused by issues outside of their control.