Is tax avoidance morally wrong?

Money and morals aren't usual bedfellows but since the Prime Minister David Cameron spoke out about comedian Jimmy Carr's involvement in a tax avoidance scheme, they've been rather uncomfortably close.

Tax avoidance has gotten everyone talking. Those vehemently opposed have been citing morality, social consciousness and the lack of contribution to society. Those remaining largely nonplussed have been relying on the fact that despite all the vitriol around the topic, fundamentally, tax avoidance is legal.