OM and Barton apologise for "ladyboy" tweet
"Joey Barton has been summoned by the Ethics Committee and will be heard on April 15," committee president Laurent Davenas told Reuters by telephone on Thursday.
Barton, who has more than two million followers on the microblogging site, has been involved in a spat with Thiago Silva this week following disparaging comments the Briton made about some of the PSG player's international team-mates.
PSG threatened action against Barton on Wednesday after the Olympique Marseille midfielder likened Thiago Silva to a transsexual and called him an "overweight ladyboy" on his Twitter feed, comments that also drew condemnation from gay activists.
Thiago Silva has not responded on Twitter.
Barton's tweet caused a stir in French media, making the front page of sports daily L'Equipe which asked: "That is British humour?"
OM have apologised on behalf of Barton
"Olympique Marseille and Joey Barton wish to apologise to Thiago Silva and his club for the inappropriate comments the English player made on social media in the past 36 hours", OM said in a statement on their website.
"Olympique Marseille officials have asked Joey Barton to end the row between him and the Paris Brazilian defender. The OM midfielder has promised to end right now the publication of any invidious comment against Thiago Silva."
Barton arrived in France on loan from Queens Park Rangers following a colourful career in England during which he spent two-and-a-half months in prison for assault during a night out in Liverpool.
At the time of the attack, he was already on bail for attacking former Manchester City team-mate Ousmane Dabo and he stubbed out a cigar in the eye of a youth-team player at the club in 2004.