The identity card is seen both as a mechanism for Government agencies to provide citizens with some set of services (in a reliable and secure manner), and as a mechanism for Government agencies to perform some set of mandated controls over the citizenry. These objectives naturally conflict, and this is part of the reason for the distrust mentioned by Aidan.
Furthermore, there is a common pattern of service providers distrusting their users/customers. Banks assume all their customers are engaged in money laundering or some other fiddle, while Insurance companies assume all their customers are in a perpetual state of moral hazard, and that all claims are potentially fraudulent.
And yet service providers expect their customers to trust them absolutely - trust them and their staff and their overseas contractors and their extremely complex computer systems. Government agencies are no different in this respect from any other service provider.
This is an example of Asymmetric Trust. See also Finance Industry View of Security.