The UK government's ID cards scheme is at risk because of huge business process demands that will hit the system - at a level comparable to the NHS's National Programme for IT (NPfIT), analysts have warned.

The cost of the scheme - currently £5.4bn, according to Home Office figures - could grow to meet the £12.4bn NPfIT price tag, IT capacity and performance consultancy Capacitas added.

A Capacitas white paper estimates that demand on the system will reach 1.2 billion business processes a year - a level that is comparable with the NPfIT system. This scale of demand is a significant risk to the project because problems with performance are more likely when demand is of this magnitude.

Danny Quilton, chief operating officer at Capacitas said: "The NHS National Program for IT has suffered from a number of high-profile performance issues over the last twelve months. These performance issues have an adverse impact on project budget, benefit and delivery timescales.

"Given the comparable level of expected demand for the UK identity cards system, similar issues are likely to surface in this project."

Capacitas said it was difficult to quantify the costs of the ID scheme, but both the level of business demand and the potential extent of the service across government departments pointed to costs "of the same order" as the NHS program.

Performance problems could hit response times or cause prolonged periods of service unavailability, resulting in project delays and cost over-runs, the report says. It adds that performance issues are "more likely to occur" when system development is outsourced.