Napoli have been docked two points as part of the on-going match fixing investigation in Italy.
The FIGC disciplinary commission confirmed the punishment on Tuesday morning, while also fining the club €70,000 and handing six-month bans to players Paolo Cannavaro and Gianluca Grava.
Their involvement stems from an allegation that former goalkeeper Matteo Gianello tried to fix a match against Sampdoria in May 2010 and asked the duo to assist him in securing a result.
Grava and club captain Cannavaro - younger brother of World Cup winner Fabio - are believed to have refused but have been charged with failing to report the attempted fix, the same infringement for which Juventus coach Antonio Conte was also suspended.
Gianello is currently out of contract and not attached to any club but was also given a suspension of three years and three months while Napoli now fall even further behind in the title race after losing their last two Serie A fixtures.
The southern club have already indicated they will formally appeal against the three rulings.
"The president Aurelio de Laurentiis, the head coach Walter Mazzarri and the whole team are calm, being confident that no violation could be attributed to Napoli," the club said in a statement posted on their official website.
"While not entering into the obsolete and outdated principle of objective responsibility, and reserving any comments on legal action for the appropriate forums, Napoli does not agree with the decisions of the National Disciplinary Committee, considering that they should not be able to irretrievably alter championships that are already in progress.
"Any decision must be made before the start of a tournament or at the end of it. There has been enough time to evaluate and make a decision since the 2009-10 season.
"We are confident that true justice can be applied to the separate decisions, based on law and equity, not on Justicialism (a theory of government involving government intervention)."
The points deduction and back-to-back league defeats mean Napoli will drop to sixth in the Serie A table, below Lazio and Fiorentina and a full 10 points behind leaders Juventus.
"There is no liability from the club," legal representative Mattia Grassani told Radio 24. "Gianello did not play a single a minute during the 2009-2010 season, yet the club has been sentenced for failing to supervise or control their player.
"I think this is an unjust sentence and completely inadequate.
"The Neapolitan club have suffered financial losses and also damages to their image and on the field of play - these are all reasons for compensation once the justice system has finished its investigation."