The scheme goes way beyond initial plans for a plastic ID card and now marks a fundamental shift in the way the government collects, uses and shares personal information about individuals, the data watchdog said last week.
Thomas said he was concerned that the government had failed to spell out the objectives of the £3.1bn ID card programme and had left issues surrounding enrolment, maintenance, verification and card manufacturing unresolved.
"Unless we are certain of the rigour of the application procedure, it is difficult to be confident that any system will workÉ The consequences for individuals arising from potential failures should not be underestimated," he said.
Thomas said that to comply with data protection principles, the government had to show why there was a pressing need for ID cards and explain how ID cards would be used in practice to combat terrorism.
He voiced concern that the scheme would give government agencies wide access to personal data without giving the public the right to check the accuracy of their register entries.
Private sector firms could build up a picture of individuals' day-to-day activities by demanding access to the population register in return for supplying services, Thomas warned.
He urged the government to appoint an independent body to oversee the scheme under the authority of Parliament. The government's plans for an ID card commissioner fell well short of the level of supervision required.