The Italian Soccer Federation (FIGC) is investigating bitter allegations flying between Juventus and Inter Milan about Sunday's clash between the sides.
Juventus won the game 1-2 at Milan's San Siro Stadium to take a commanding 12-point lead at the top of Serie A.
After the game Inter boss Roberto Mancini claimed Juventus' Pavel Nedved dived to earn the free-kick from which Alessandro Del Piero scored the winning goal. On Monday Inter's Portuguese star Luis Figo accused
Juventus General Manager Luciano Moggi of meeting referee Gianluca Paparesta in his changing room before kick-off.
Moggi replied that Figo was lying and said he should be banned.
Juventus reported the matter to FIGC, describing Figo's comments as "serious and absolutely unfounded".
FIGC opened a probe on Tuesday.
Inter hit back on its internet site, branding the Turin club's action an "inappropriate act of arrogance".
It also vowed to "defend the reputation of its player in court" and demand "punishment for whoever has called into question his honesty and rights to freedom of speech and expression."
Pundits say there is a real risk the matter will be dragged through the civil courts.
Tension was already high before Sunday's match.
Inter players and officials had claimed there was something fishy about a refereeing mistake the week before
that enabled Juve to beat Udinese 1-0, courtesy of a Del Piero goal scored from an off-side position. Many Italian soccer fans believe referees feel intimidated by the power of the mighty Juventus, which has won 28 league titles, and frequently give it the benefit of the doubt when making decisions.
For its part, Juventus is reportedly preparing a dossier documenting all the incidents in which Inter has profited from referring errors this season. The furore is only the latest in a string of controversies between Inter and Juventus about refereeing.
The most infamous incident took place during a scudetto showdown between the sides in 1998.
Inter fans claim that in that match Ronaldo was denied a clear penalty, play continued and the move concluded with the referee giving a penalty the other way only seconds later. Juventus won the game and went on to take the title.
On Tuesday Mancini was handed a one-match ban and a 5,000-euro fine for the verbal abuse he directed at Paparesta at the end of last weekend's Inter-Juventus game. Juventus Vice President Roberto Bettega was also given a 1,000-euro fine for entering the players' tunnel without permission.
