Let's break this down a little.
First of all, the main selling points for this utopian dream are tax evasion and illegal immigration.
In terms of tax evasion, the latest figures show an assumed "loss" of revenue to the treasury of 5.5 Billion pounds. To put this flight of fancy into perspective, the total "Tax Gap" for that year was estimated to be 46 Billion pounds, with small businesses being responsible for over 80% of this. Basically, cash in hand jobs and fudging the books, including lawful, tax avoidance.
So, if fully implemented, at a cost of (London School of Economics estimated) 12 to 18 Billion, it would just about pay for the Department of Cultures annual budget, that's if the scheme were to ever "turn a profit", which considering the government's track record with large projects is unlikely. HS2 anyone!
The cost of this implementing this scheme, coupled with the estimated "savings", just don't make sense.
As for the illegal immigration argument, most illegal migrants declare themselves at the earliest opportunity, they want to be registered an given paperwork. A national I.D card just makes their lives easier, less paperwork. It would just encourage more to come, because the logistics of living here while your claim is waiting to be approved would be so much easier (over 50% are, and of those denied, less than 30% have ever been removed, most of those were voluntary).
Those "hiding in plain sight" would only be found if police were given the powers to "Stop and I.D", literally a "show us your papers" society. Considering the levels of corruption and ineptitude in policing, do we really want to give that power to the police?
Without it, I.D cards would be worthless, as those who want the claim the right to work wouldn't need one, and those who want to hide wouldn't use one.
What national I.D cards do, which all previous posters saying "but I had one in the place I lived in, you get used to it" fail to understand, is they provide a central data point to link everything else to.
Your national I.D card is nothing more than a QR code that links your file to every other government record of you. HMRC, medical, banking, Internet history, GPS location from your phone and car, Passport and various others. All these data points could then be stitched together digitally, providing complete oversight into every aspect of your life. This is the bit all other countries didn't implement, when people talk about the benign nature of I.D cards, that is why they didn't seem too intrusive.
If you have a car built after 2023 you will have a "connected vehicle", I'm willing to bet none of you bothered to read the T&C when you linked your phone to the infotainment system. If you have a Kia, Ford, Peugeot, BMW, whatever, you WILL have signed up for your "Driving Safety Score" and vehicle data, including GPS location and speed, to be made available to "Government Bodies". They even spell out that "Geofencing" is "only to be used under Instruction from Government Authorities".
A national I.D card is just a mass surveillance strategy. It's not about saving money or reducing immigration. It will be a electronic tag on everyone. Once introduced, you WILL begin to see the "environmental problem" pushed like Covid. The old "give people something to fear and you can get them to do anything" mantra.
Flying too much!
"BAD CITIZEN" we will use your linked data to block you from paying for any more flights!
Buying too much alcohol!
"BAD CITIZEN" we will stop your card being used to pay for alcohol. It's all for the good of the environment, and the NHS. All hail the NHS!
We saw from your online history that you support the planned anti-government protest planned for next weekend!
"BAD CITIZEN" we will stop your card from paying for public transport and "geofence" any vehicle you are detected to be travelling in. Can't have you criticising the Government. It's all for the good of the environment, and PUBLIC SAFETY. We want all citizens to be SAFE. It's important to feel SAFE. Don't worry, we will keep you SAFE!