Food banks

I 've had my say about these (3/6/13) and I won't rehash what I said then, but apparently their usage has increased significantly over the last couple of years and this is being presented as evidence of an increase in poverty.  I've had my say on that too (13/6/09) but the question it seems to me is whether this increase is supply-led or demand-led.  In other words is the number of food banks increasing because more are needed, or are they being used more because there are more of them? I imagine your view will depend on your political stance.