Former leader Umberto Bossi, his son Renzo and former treasurer Francesco Belsito were convicted for fraudulently obtaining the huge sum in electoral expenses for the then Northern League from 2008-2010.
Following the guilty verdicts, a court in the northern city of Genoa tried to recover the money but could only find €3 million. The Supreme Court in April sent the case back to Genoa, which on Thursday issued its ruling.
League lawyers insist the party currently has only €5.5 million, which come from donations, and that they might take the case back to the Supreme Court.
Firebrand anti-immigrant Interior Minister Salvini, who turned the party into a national political force in the wake of the scandal, has repeatedly said he never saw the missing millions. At the time, he was a member of parliament and then member of the European parliament, as well as vice-secretary of one of the party's regional branches.
"This is an affair from the past, I hope that the Genoa court will spend more of its time on the matter of the collapsed bridge," Salvini said after the court decision, referring to last month's disaster that killed 43 people.
"If they want to take everything away from us, then do it, we will continue with our political work, because we have Italians at our side," he said.
The League won 17 percent of votes in March elections, but the latest opinion poll predicts the party would win 30 percent today.
- Political cheat sheet: Understanding Italy's League
- Matteo Salvini: Who is the firebrand politician shaking up Italian politics?
- League leader lashes out over frozen bank accounts
Umberto Bossi was sentenced to two years and three months in prison for using more than €200,000 in financing provided by the state to political parties to fund an extravagant lifestyle.
Renzo Bossi was convicted of embezzling more than €140,000, including several thousands to pay traffic tickets and €77,000 to buy a diploma in Albania, and given a one and a half year sentence.
Belsito received the longest sentence of three years after being found guilty of defrauding the state of nearly half a million euros.
All three deny the charges and are in the process of appealing. If their convictions are overturned the funding would be returned to the League, but prosecutors argue that it is necessary to freeze the party's assets now as a precautionary measure.
Bossi, meanwhile, continues to represent the League in the Italian Senate.