"If a mother lets her child go hungry because she chose to have 6 kids and spends her benefits on Sky and mobile tariffs,nights out at the pub etc then really there isn't much anybody can do."
Ah, so you think even if benefits were capped at, say, 2 children per family, there would be enough money provided that the woman spent it sensibly and didn't fritter it away on sky tv and mobile phones?
Can I point you in the direction of George Orwell's 'The road to Wigan Pier', if you haven't already read it? There's nothing new under the sun.
I do not think there would be enough money under a revised system, even if the entire family existed in a limbo of no TV, never going out, never buying a gift or having a life. And I think that inflicting that kind of social exclusion on people in modern society is unacceptable even if it means they can eat (presumably potatoes) and buy shoes. And a recipe for social unrest.
It simply makes no sense to punish a generation of children in order to stigmatise their parents.
If the state's aim is to reduce the number of children it supports in the future there is no quick fix. It is no more acceptable to withdraw support from existing children in families than it is to remove them from those families.