In principle I think ID cards are a good idea: the potential to combine a passport, driving licence, proof of age, and basic medical history in one place is a good idea.

There are some massive issues that would have to be addressed such as security.

To prove that any idea can be screwed up by the government, they've manage to ensure the cost is vastly more than planned and the uses are almost nil - what are they for exactly?

Making them voluntary is the last farcical play of the idea: it'll catch terrorists, criminals and asylum seekers who decide to purchase a £30 card and carry it with them... Hmmmm. Unless these three groups are suddenly overly law abiding and brain dead this isn't going to happen.