The Brazilian was initially handed a nine-month ban over the incident that followed a Ligue 1 clash with Valenciennes on May 5, but the FFF's High Commission has now imposed a sterner sanction that will expire on June 30, 2014.
"The High Commission of Appeal of the French Football Federation on Wednesday decided to suspend Leonardo, sporting director of Paris Saint-Germain, from all official activity until 30 June 2014," read a statement on fff.fr.
Leonardo's initial ban had been due to expire on February 8, 2014, a sanction PSG branded as "unjustified and extremely harsh".
The club launched an immediate appeal but that has now backfired, with Leonardo facing an additional four and a half months on the sidelines, during which time he cannot be present on the touchline, in referees' dressing rooms or at any official functions.
The increased punishment also threatens to severely dilute his influence with new PSG boss Laurent Blanc, who has replaced Carlo Ancelotti.
Leonardo is alleged to have barged into referee Alexandre Castro in the tunnel after the Valenciennes match and has been provisionally suspended since.
The 43-year-old had claimed he was pushed into the referee by the principal match delegate Marc-Gerard Biolchini, but the disciplinary committee that initially ruled on the matter decided his action was deliberate.
Leonardo was outspoken in his criticism of referees last season and described the sending-off of defender Thiago Silva in the Valenciennes match as "unacceptable".
The French champions were also handed a suspended three-point deduction for next season, but the FFF High Commission elected to pass on the club's appeal against that sanction to the Ligue de Football Professionnel (LFP), who first handed it down.
"Concerning the removal of the three-point deduction on PSG, the Commission decided to refer the matter to the Disciplinary Committee of the LFP," the statement concluded.