Concerns over the entitlement card scheme for accessing government services, which was outlined in a recent Home Office consultation paper, include the potential for excessive state monitoring of individuals' activities and the risk that the cards could be targets for identity fraud.
"The government's efforts to consult widely on its proposals are welcome, as is its recognition that for any scheme to proceed data protection and privacy concerns must be addressed," said information commissioner Richard Thomas.
"However, the present proposals raise a number of serious concerns that must be remedied if the scheme is to meet the requirements of the data protection law."
A national entitlement card scheme would probably involve smart-cards to store citizens' personal details, including a unique ID number for each card holder and a central register of authorised card holders.
Other concerns raised by the information commissioner include the need to keep personal details accurate and up to date.
The proposed scheme could cost up to £1.5bn to implement, with experts warning that could pose severe technical challenges.