Not really. Avoiding tax means you are explicitly arranging your affairs in some more complicated way, for the primary purpose of reducing how much tax you pay - but that all of those mechanisms are legal. The issue is that some avoidance is just common sense and some is obviously devious.
What's that quote about "I can't define right and wrong but I know them when I see them"? Clearly, the legal system has to work to the letter of the law but that doesn't mean some cases aren't very obviously taking the mick - while others look fine to some and dodgy to others.
For instance an IT contractor working through a Ltd company (because agencies aren't happy if you work as a sole trader) can balance their income between company dividends and salary as they see fit. How can you possibly draw a line where that balance becomes 'wrong'?