priggish [prig-gish ]
1 Self-righteously moralistic and superior; demonstrating an exaggerated conformity or propriety, especially in an irritatingly arrogant or smug manner.
"Any little assistance," he continued with the same queer, priggish accent, "that may obviate the necessity of my communicating with the family." (G K Chesteron, The Wisdom Of Father Brown )
What can you do but laugh at the fact that Lewis could persevere with such a priggish demeanour when now it seems he was cooking the chemicals just as keenly as poor old Johnson, a man socially backward and easily led - and treated with the same notoriety as a war criminal in the days and weeks after the Seoul 100 metres final? (Keith Duggan, Carl Lewis' feet of clay leave a squalid trail, The Irish Times, 2003)
Those poor stupid fanatics have ben sold on the idea that what they want is the ability to give themselves a little priggish congratulations over having done the right thing. They’d rather be right than happy (John Barnes, A Million Open Doors)
From prig, 'precisian in speech or manners,' 1753, originally in reference to theological scruples (1704), of unknown origin; earlier appearances of the same word meaning 'dandy, fop' (1670s), 'thief' (c. 1600; in form prigger recorded from 1560s) could be related, as could thieves' cant prig 'a tinker' (1560s). (Online Etymology Dictionary)