I would have more faith in ID cards if I felt the government had any success with their other projects.
Things like the CSA, removing asylum seekers, the NHS computer system, removing foreign criminals, controlling our borders, the list goes on.
Honest people will get their card and carry them round with them all the time.
Dishonest people and illegal immigrants will get stolen cards or forged cards, or not carry a card at all, and if they get stopped will run for it, or shot or stab the policeman.
Even if someone is found with a stolen card, or a forged card, they will not go to prison because they are all full.
We have a history of incompetent government schemes (although this current lot are the worst), so it will not have the desired effect, and it is doomed to failure