For the majority of politicians, I cannot see what principles their policies evolve from.
That's the way it works, isn't it? You have the fundamental principles and develop policies that will accord with them, suited to the ongoing conditions and needs of the community.
So, when the phrase 'unprincipled lot' is used, it means their policies are ad hoc, off the cuff - not developed from principle.
So, what's a principle? Short & embracing a wide area; e.g. Love thy neighbour as thyself ... from which, maybe, a lot of the old Common Law was developed.
However, it seems that most politicians are either afraid to enunciate their principles in case the populist vote mis-understands them or maybe because they just don't have any .....
Whether it's the BNP, the Tories or Labour: not any idea at all what their 'principles' are, but I suspect they're all garnering support only from people who seek their own benefit.
I don't admire 'democracy', nor do I have an alternative!