That's exactly what high marginal tax rates (or loss of benefits rates) causes.
People make an informed choice about what working harder/longer is "worth" to them in other than monetary terms. If they'll "only" earn another £100 from an extra day's work (after taxes, travel costs, loss of benefits etc), then they may well think that a day of leisure to do other things is worth the "loss" of "only" £100.
And in fact, there are lots of instances, where working an extra day (or even an extra hour), or taking a promotion, etc. or getting a better job further away (or more difficult to get to) may actually make them worse off in monetary terms too!
It's all well and good telling people to think of the long term, etc., but if they can't afford to live in the short term, then they're in no position to look long term!
Personally, I think we need to start looking at things like income tax relief against wages for child card costs, commuting costs, etc as they do in some other countries, to help "make work pay" rather than constantly regarding workers as cash cows to pay for the non workers!