But the Board of Internal Economy also determined that it won't be possible to reimburse taxpayers because the bylaws weren't clear enough at the time the money was spent.
"The board believes that the use Mr. Duceppe made of the House resources that were available to him was inappropriate," the Commons governing body said in a statement.
"However . . . the board finds it impossible to take any disciplinary action."
For more than six years, Duceppe paid Gilbert Gardner, the Bloc's director general, out of his parliamentary budget.
The ruling said the text of a key bylaw governing the use of House resources was not "rigorously defined," leaving it open to different interpretations.
The bylaws have since been revised.
Still, the Conservatives are calling on either Duceppe himself or his party to pay back the money.
"I think the appropriate thing would be for Mr. Duceppe to consider, or perhaps the Bloc to consider, repaying some of these funds — maybe all of these funds," said Conservative MP Gordon O'Connor, who sits on the board.
"Even though they are following the letter of the law, they're not following the spirit."
Duceppe insisted before the board in February that he did nothing wrong, and that Gardner's salary was paid within the context of House of Commons regulations.
The former leader stepped down after he lost his own Commons seat and the Bloc was almost wiped out in last year's federal election.
Bloc MP Andre Bellavance didn't sound swayed Tuesday by O'Connor's exhortations.
"The board of internal economy just said that nothing was wrong about what Mr. Duceppe did at that time," Bellavance said.
"Nothing is said by the board to pay back the money."
News of the payments to the party executive broke just as Duceppe appeared to be gearing up for a run at becoming leader of the provincial Parti Quebecois.
A short time later, Duceppe announced he was getting out of politics entirely.
Also on HuffPost