Deceitfully

from WordNet (r) 3.0 (2006)

deceitfully
    adv 1: in a corrupt and deceitful manner; "he acted dishonestly
           when he gave the contract to his best friend" [syn:
           {dishonestly}, {venally}, {deceitfully}] [ant:
           {aboveboard}, {honestly}]

from The Collaborative International Dictionary of English v.0.48

Deceitfully \De*ceit"ful*ly\, adv.
   With intent to deceive.
   [1913 Webster]