The Treasury told us that the lack of transparency from NS&I had made it difficult for the Treasury to understand the reasons for the cost increases, saying it was not always clear whether the funding NS&I received was being used on the Programme or running NS&I. It also said NS&I had been “sluggish” to respond to conditions that the Treasury had set as part of the business case approval.77 NS&I told us that the transformation programme affects its whole business, including all its IT, operations, customer services and products. It claimed it was able to give the information on cost to the NAO, but the NAO report says it had proved “challenging to identify spend to date, and forecast spend for the remainder of the Programme”, and the cost estimates should be “treated with caution”.78