I was listening to a piece on NPR about a move to introduce some sort of code of ethics into the guild of economists. Many economists resist this sort of thing because they view their trade as a science, a matter of "fact" rather than "value," a matter of "this is how it works" rather than "this is what we should do."
Actually, it is this last contrast where some economists contradict themselves. I agree that economics is a science--if you do this, such and such will happen in consequence. An economist can thus suggest that "if you do such and such," "such and such will happen." Of course there are different schools and so we cannot speak of a consensus on many things, but the basic sense of the discipline as science is clear.
It is when the question of "should" that ethics inevitably becomes part of the process. Boyer, in his Idea of the Christian University, wisely suggested that it was at this point that a person's Christian values became a part of the equation. For example, an economist might say--this particular course of deregulation or this particular bank failure will create great economic crisis in the short term, but will result in a more stable market sooner, while more moderate regulation and a bailout will result in a slower and less substantial recovery, but fewer people will commit suicide, so to speak. (I'm not speaking to the specifics of recent events or the Depression, only trying to give a general impression).
It is at this point that those implementing economic principles, whether it is economists suggesting a particular course of action or the political system, bring ethics into the equation. The implementation of economic theory always and inevitably involves ethics.