Crystal Alliance was given a multimillion-pound contract including dealing with customer complaints and has invested heavily in its call centre arrangements.

But NIW chief executive Laurence McKenzie said it was time to look carefully at the arrangement.

"One of the things that keeps me awake at night is the impetus we need to give to customer service," he said. "We have far too many at the minute, I believe, hand-offs and hand overs for the customer. We have an outsourced call centre who then try and hand the customer's problem into the organisation and I think we need to look very carefully at that, at our processes.

"We have recently appointed a very experienced person in this area who I think will bring a lot to the organisation."

Mr McKenzie was giving evidence to Stormont's Public Accounts Committee.

A total of £27 million was paid to Steria Ltd, the prime contractor for Crystal Alliance, in the past two financial years, 2007-08 and 2008-09. The range of services that Crystal Alliance has provided includes customer contracts and services, non-domestic billing and the provision of a mobile work-management system.

Fred Cobain is chairman of the Assembly's Regional Development Committee which oversees water provision regularly.

"Crystal Alliance won the competition, it would be extremely difficult now to bring that into the department (NIW)," he said.

"They probably paid a lot of money for new technology and to train people, they would not have done that without long-term commitments."