Leonard Watters was today sentenced to six months over the allegations, for which he later apologised.
District Court Judge Dermot Dempsey said: "The public must be protected from this type of untrue, unfounded allegations. He put the injured party through a lot of pain and anguish."
In June last year, Watters claimed that he had been groped by the X Factor judge in the bathroom of a Dublin nightclub.
Only a week after making the allegations, he dropped his charges against Walsh, leading to his subsequent arrest.
Boyband manager Walsh last July admitted that he considered suicide following the claims, insisting that the ordeal has affected his personality forever.