ANY amount of work. Yes they do start reducing your benefit if you earn more than £20 but it's not pound for pound so don't be scared.
For example. last year I was on HB during the summer and then I worked part time. I earned around £250 a week and my HB was reduced by £20 a week. xx
good for you but this system really makes no sense
I'm not even in the UK so what would I know
But I can see the sense in it - part of the problem many people have with the benefits system is that they make it so that it's not worthwhile for people to work at all. If you earned 250 quid a week and lost, say, 200 of your benefits then many people would think it not worth the trouble of working 25 hours or whatever just for 50 quid.
Also, if you are nowhere near the top of the salary limit for receiving benefits, then you may be able to earn quite a lot before your benefit is cut back severely.
I don't get benefits and I pay quite a lot of tax where I live but I can see the sense in the system, well, in that part of it at least! If it's worthwhile for people to get back into the workforce gradually, it does a lot more good than basically discouraging them from working AT ALL.