Devils Advocate question here: how has the two child cap affected behaviour? Who has made different choices based purely on the cap? Would these people have made different choices without the cap?
My feeling is that in reality, the number of people this is, is actually surprisingly small. If anything it probably has changed the mentality of slightly better off families more than the poorest, because this is as much about attitude toward being responsible rather than being responsible.
By that I mean, people who aren't really arsed and don't really take responsibility aren't going to suddenly start taking responsibility if you take a bit of money off them for irresponsible decisions. They are still going to be irresponsible.
Whereas people who would be most likely to change are the most risk adverse. And those who it will financially affect but really want children will prioritise and value the children more than the loss of money and will take the attitude that they will 'cope' regardless. And they would have taken responsibility regardless but wouldn't be in poverty and much more vulnerable.
I think that yes, we should be financially responsible for our own children. But that's my value and my priority in life and the problem here is that different people don't prioritise that. Financial penalties are unlikely to change that mentality and there's no evidence works.
If you look at the aim of the policy - to make parents take more financial responsibility for their children, I don't think it's achieved it. If it had achieved that, parents would be working more hours and be better off financially.
Instead in practice it's put families who are struggling in a more financially vulnerable position - so if they have an unexpected bill - they tip into the spiral of debt that's so difficult to get out of. It's not about a lack of willingness to take financial responsibility - its a lack of ability to and a lack of opportunity to. And it's ultimately made families less financially responsible and more dependent on things like food banks.
The cap leading to more children being in poverty certainly does not looking like parents have been encouraged to take greater financial responsibility or if they have been encouraged they haven't achieved that goal.
So the question is, is it worth carrying on with a policy that's known to be ineffective?
If those families had the extra money what impact would it have? Would it give those children better long term prospects in someway? Whether it be health related or economic.
If so, whilst it may be more costly is the benefit to society as a whole greater than a policy that encourages desperate poverty?