Lebanese President Emile Lahoud has been excluded from a summit of French-speaking nations in Romania.
Lebanon has accused Mr Chirac of meddling in its domestic affairs
The move came after a UN report on the 2005 murder of former Lebanese PM Rafik Hariri implicated Syria and Lebanon, who deny allegations of involvement.
Addressing the 63-member group, French President Jacques Chirac said the move was "in keeping with UN decisions".
The pro-Syrian president accused Mr Chirac of being responsible for excluding him from the summit.
In an interview with Radio France International, President Lahoud said the French president was "meddling with Lebanon's domestic affairs.
"His [Mr Chirac's] move is unprecedented by a head of state and harms principles of Francophone and the historic and deep-rooted relations between Lebanon and France."
Romanian President Traian Basescu, speaking in the capital Bucharest, said he had made the decision not to invite the Lebanese president to the summit known as Francophonie.
"I think it was correct given the suspicions in the [UN] report about the death of the former premier Hariri," Mr Basescu said.
However, Mr Lahoud dismissed the Romanian leader's claims and said he was excluded for personal reasons relating to Mr Chirac's well-known friendship with the late Mr Hariri.
Romania extended an invitation to Lebanese Prime Minister Fouad Siniora - who declined to take part, sending the culture minister instead as "his personal representative".
The summit, which is held every other year, seeks in part to counteract the trend among youths worldwide to learn English instead of French.