The fundamental issue with tax credits, though, doesn't really have to do with deserving/undeserving or feckless/responsible: it functions as a ludicrous job creations scheme for the civil service - why on earth is the government taking tax from those with families on the minimum wage with one hand, and then giving them payouts with the other.  

Let's cut out the middle man, and just not take it off them in the first place: because by doing so, we end up subsidising (in the main) big businesses - like Tesco or MacDonald's - who pay poor wages.  They continue to make their shareholders profits, but that is because their wage bill is subsidised by us, the tax payers.  I'm fairly sure this sort of sharp practice used to get people doing time for fraud...

Absolutely, people ought to exercise personal responsibility, and I am certain that the vast majority of people do, in fact: that's why it's news when benefits' cheats get busted, or someone with 12 kids say that they and their partner aren't going to work.  They are the exceptions, not the rule.  I am certain the majority of people with kids would far rather not bring them up in relative poverty, live hand to mouth or worry about paying for uniforms, trips and birthdays etc.  I had a student who has a daughter (rather a surprise in his first year of study, for him and his wife) but is adamant that if they have another child, they will only have one: he grew up in a family of four kids, and saw how his parents struggled, and how they couldn't go on school trips etc because there was never the money - he's determined his kids will never have to miss out because there's not enough cash for too many kids: I honestly feel more people are like him than those who breed recklessly and indiscriminately.