There's three groups:

First, a vocal minority of security freaks lead by Tony Blair who think that forcing everybody to carry ID cards around is a proportionate way to protect Britain from terrorists, illegal immigrants and other foes.

Second, a large proportion of the country who think that the introduction of optional ID cards is a slippery slope towards the first group getting what they want.

Third, another large proportion of people who think that the risk of the first group getting what they want is overblown, or else think that the convenience of being able to prove identity more easily outweighs the inconvenience of having to carry an ID card around everywhere.

In the great ID card battle of the late-00s, the second group won decisively and politicians have been too scared to take up the issue ever since. Except for Blair, but having the face of your political campaign be a war criminal is of negative value to that cause.

I wouldn't describe myself as a very very vocal person, but I'm not a fan of the UK introducing identity cards as it would almost certainly be misused by the government and the data would be leaked as the UK government is utterly incompetent (when it comes to computers).

Voter ID rears its ugly head.

It's compulsory now so it's doable. Especially since voter registers are available to certain companies* regardless of the voters' consent.

*eg political parties, credit bureaus.