The BCS said early signs of confusion about scope and requirements lie in the government's consultation document. It said many studies have shown that clearly defining the scope and requirements of an IT project at the start is crucial to success.
The BCS pointed to its own recent major study with the Royal Academy of Engineering, which took evidence from more than 70 experts from industry and academia.
"Requirements definition is one of the critical and most challenging stages of an IT project," the report said. "Many projects fail because of flaws in the elucidation of requirements. Requirements capture seems seldom to be approached with the rigour necessary for this critical process to be accomplished effectively."
The ID card project needs tightening up in this crucial area before it gets under way, the BCS said. "There does not seem to be any firm or fixed statement of what the system is meant to achieve and what scope limitations are to be imposed," said external relations director Mike Rodd.
The government's consultation document on the scheme initially puts emphasis on reducing fraud and later switches to counter-terrorism, Rodd said. Immigration control, dealing with illegal workers and stamping out abuse of the NHS are also mentioned.
"It is important for the project's success that there is a primary motive - the problem that the ID card system sets out to solve," Rodd said.
"There is a lack of common understanding of what the system is for and what it is trying to achieve. If you do not know exactly what the card is for, you cannot design the system."
Details of the operation of the ID card system also give the BCS cause for concern about the definition of requirements.
"The early emphasis in the consultation paper is on iris and fingerprint recognition, but later facial recognition emerges as a prerequisite," Rodd said. "Which method is actually preferred?
"There is reference to a family of possible ID cards, including a passport, a driving licence and a new ID card. This, again, makes the project definition unclear."
Rodd added, "The government's own advisory body, the Office of Government Commerce and the National Audit Office have identified the top cause of project failure as being the lack of a clear link between a project and the organisation's key strategic priorities.
"We believe that this link and the resulting project scope and requirements have not been clearly established and that this puts the whole initiative at risk."
The BCS is putting its concerns and advice to the Home Office in written and oral evidence.
The report by the BCS and the Royal Academy of Engineering, "The Challenges of Complex IT Projects", is available from