A High Court judge has rejected the majority of a preliminary appeal by Accenture aimed at blocking a £182 million lawsuit by British Gas over a troubled SAP-based customer system implementation. The case will go to court.

But the judge upheld Accenture's argument that there was an important difference between system errors that caused problems and those that "could" result in problems. The overturning of that previous judgement could make it more difficult for British Gas to blame Accenture for those errors and to hold CIO 100 listed Accenture liable for fixing them, the supplier claims.

In the case, which is only at the preliminary hearings stage and will reach court in October 2011, British Gas parent Centrica is claiming £182 million from the IT supplier, saying the billing system Accenture implemented was fundamentally flawed and caused "huge disruption" for the company and its customers.

Accenture denies the claims, saying the system met all contractual requirements, was delivered on time and on budget, and that British Gas approved the system after extensive testing. The lawsuit then emerged two years later with British Gas "mismanaging" the system, it says.

British Gas says the "inadequate" system caused "millions of errors", affecting services and losing the company customers. Incorrect bills were sent to customers as a result of problems on the 'Jupiter' system, British Gas claims, and customers then had to make lengthy calls to correct the problem.

Accenture argues that instead of its own errors, the major problems resulted from British Gas' running of the system, after the utility took over. The IT supplier argues that there were also deliberate exceptions built into the system, for when bills needed to be manually reviewed, and says these are not errors.

In an appeal judgement handed down on 30 July, the three High Court judges on the case uphold nine out of 10 preliminary issues that were ruled on by the court in November.

In the issue that was overturned, the appeals judge states there was a difference between defects that "cause" an adverse effect and those that "could cause" that effect.

Phil Bentley, managing director at British Gas, said the company was now "one step closer to holding Accenture to account for the disruption caused to our customers".

But Accenture insists its side of the story will be upheld at trial. "What British Gas didn't mention in their statement is that the Court of Appeal in fact accepted a number of Accenture's arguments," said a spokesperson.

The judgement in favour of Accenture was a "key issue" and would "make it more difficult for British Gas to attribute its problems with the system to Accenture, rather than taking responsibility for fixing them itself", the spokesperson said.