I'm a crusty pre-tennis-court conservative, but I must confess the Middlesex University report that says we shouldn't come down too hard on the black economy struck a chord.
My text is from Burke (speech on American taxation, 19 April 1774): "no vulgar precaution ought to be employed in the cure of evils, which are closely connected with the cause of our prosperity".
We encourage a flexible labour market, an eye for the main chance, and willingness to graft for wedge. These qualities make us rich; but they also stimulate some of us to activity in the off-book world. The qualities that make us rich conduce to rip-offs too.
It's the same with corporate tax avoidance. For every ten clever chaps in the City making an honest buck, there's always one with a mind that runs to diddling the Revenue. If there were a magic spell to make them stop, then we'd use it. But there isn't.
Some abuse is the price of freedom. And freedom is, inter alia, a precondition for wealth.