The disclosures about expenses claims made by MPs have been met by the insistence that what they did was "within the rules" and that all the items were scrutinized and approved. This may be true, but it fails to answer the public concern at what has been going on. The nub of it is that MPs have deceived the public for many years by awarding themselves much higher salaries than they have admitted to. They did this by keeping the headline figure down, and awarding themselves a "stealth salary" of padded expenses to augment it.
MPs of all parties have connived in a system which reimburses them for items like bathplugs and barbecues which other people have to buy from taxed income. As the 'expenses' are tax-free, the effective salaries received by MPs are even higher. The public wants to know how MPs, who make laws telling other people how to behave, could behave so deceptively and dishonourably themselves. The answer seems to be that, like the bankers who give themselves multi-million bonuses to reward their failure, they do it because they can. They have the power to do it, and they regard that as a right.
There is a general feeling among the populace that people who occupy positions of authority should possess sufficient probity to restrain them from misusing their powers. They should have a sense of right and wrong sufficiently well-developed to keep them from tawdry and discreditable self-seeking. "With great power comes great responsibility," as Spiderman's uncle cautioned. The fact that MPs and bankers can award themselves unmerited sums of other people's money does not mean that they should. On the contrary, their occupation of those high seats of authority means that they should not. And the higher the office, the greater is the standard of moral correctness required.
The problem for both MPs and bankers is that they have not shown the moral stature required to accompany those positions.