The thing is, nothing in this plan is a new idea.
It’s all been suggested and considered before and rejected for the many good reasons set out on this thread.
Children (and adults but let’s focus on children for a minute) need a lot of things other than food. If parents are only allowed to buy food and items that are necessary for mere survival, many children will really suffer, and it will only increase their likelihood of living on benefits themselves.
And people will always find a way to get addictive substances even if through crime. Prohibition taught Americans that.
People are in favour of this because the general COL is so high that waged people feel the pinch and want to know that those who are unwaged are worse off than them. What we need are policies that benefit everyone, that bring us out of the economic dire straits we’ve been in for some time.
Edit - and yes you can bet if the Tories did get in and do this, they’d be lucrative contracts for their mates, and massive restrictions on which outlets could be used to buy food (to the benefit of their mates!). Probably fees levied to use the cards and all sorts.
Then the black market for cards bought at less than face value in exchange for drugs etc…