@Bambamhoohoo
They will always be better off earning more
That's not the case though. There are plenty of points on the income scale where loss of benefits along with taxes on extra income can make you worse off.
And even more instances where, yes, you'll be better off in purely tax/benefits terms, but when you factor in child care costs, commuting costs, etc., you do end up worse off.
I'm a long advocate for a "maximum" marginal rate (tax and loss of benefits) of 50%, so that whatever income level you're sat at, working an extra hour, shift, day, etc will guarantee you can keep at least 50% of it, having taken account of loss of benefits, taxes, etc. If you know you're going to lose over half of your "extra" wage, it's a massive disincentive to actually bother doing it, bearing in mind child care, commuting, AND loss of your personal enjoyment time.