Quite simply, ID cards are there to track and monitor the British civilian population. Most of us have photo ID in the way of a driving licence or passport.
We're fed the line that they're being introduced to tackle crime and terrorists. Well criminals and terrorists have the resources to forge ID cards much as they did with passports.
The irony of all this is the lengths that the MPs, PM and the Speaker went to, to block the publishing of their expenses (and even when they lost the last battle they wanted to take a black marker pen to them) and the instigator of the cards was the 2nd Home Secretary who looks like she'll be before the magistrates for it.