Paris St Germain have criticised Joey Barton after the Marseille midfielder used social networking website Twitter to liken Thiago Silva to an "overweight ladyboy".
In a series of tweets published through his official account, the on-loan QPR player questioned whether Brazilian defender Silva was "pre-op or post-op" and demanded an explanation why the 28-year-old had mentioned him in his pre-match press conference ahead of Tuesday night's Champions League quarter-final with Barcelona.
The Ligue 1 leaders expressed their unhappiness with Barton's "unacceptable remarks" and threatened to "take action" against the former England international.
A statement published on psg.fr read: "In the last few hours, on social networks, unacceptable remarks have been made by Olympique Marseille player Joey Barton against Paris St Germain player Thiago Silva.
"These attacks are serious and go beyond mere verbal jousting.
"The directors of the club, the players and the coaching staff are supportive of Thiago Silva and cannot accept such statements.
"They reaffirm their unwavering commitment to the values of respect that should govern our sport. Thiago Silva and Paris St Germain reserve the right to take any action they deem necessary."
PSG have taken issue with a series of tweets against the player which began to appear on Barton's account from Tuesday afternoon. Barton originally tweeted: "Thiago Silva. That the same p**** thats been injured all season. Another over rated Brazilian. Sort your hamstrings out FatBoy."
The Liverpudlian was responding negatively to comments from Silva ahead of the game at the Parc des Princes, which finished 2-2 ahead of next week's second leg at the Nou Camp.
He continued tweeting during the game, adding: "Have to take back what I said about Thiago Silva being over rated today. Been immense tonight. Still looks like a overweight ladyboy though!"