Use the adjective irreproachable to describe something or someone blameless or not deserving of criticism. It can be annoying, but your parents strive to give you irreproachable advice when they tell you, "Study hard in school," and not "Party on!"
The adjective irreproachable comes from the Old French word reprocher, which meant "to blame." With the addition of the prefix ir-, meaning "not," and the suffix -able, meaning "capable," we get the English meaning of "not capable of being blamed." It is the rare politician who has an irreproachable reputation. So if your background is not irreproachable and you run for office, be prepared for the press to dig up all the skeletons in your closet.