"I don't think there can be many mothers who wouldn't buy formula because they didn't have a specific voucher for it, instead spending their money on booze and fags. And if they are, a voucher is unlikely to turn them from 'take the child into care' into 'mum of the year'"
No, of course there aren't. And of course it won't. But they do exist, and it generally takes a while before a neglectful mother either turns the corner or is deemed unfit enough for care proceedings. Their babies matter, too. It's also worth remembering that benefits are swingeingly low, and if you just add that money into the overall pot, it may have to be used to pay the gas bill, if fruit/veg is the other option. That doesn't make a mother irresponsible, it just makes her very poor. Vouchers mean it is ring-fenced.
"that would be far far better, for those poor unedcuated souls who don't /won't breastfeed."
What, than vouchers that mothers can spend on milk and fresh fruit and veg for themselves if they breastfeed, or milk for the babies if they don't? This money only goes to mothers on benefits - they need it, IMO! I think more cash supporting bf is essential, but I strongly disagree that the right place to find it is the healthy eating benefit given to mothers of under-3s on the lowest income in society.
"FFS - pregnancy is a choice, let them get on with the consequences. "
Then I assume you aren't accepting your health in pregnancy grant, child benefit, or child trust funds. Or is your own choice somehow different?