In an apparently rare legal action of a state suing an individual, Qatar has filed papers against Florian Philippot, a vice-president of the National Front, in a French court for defamation.
The legal action was confirmed in a statement released by Doha.
"The State of Qatar has filed a defamation complaint against Mr Florian Philippot," read the statement.
"In the hours following the Paris terrorist attacks of January 2015 Qatar condemned these acts in the strongest terms, affirming its support to France and its solidarity with the victims. Qatar continues to do so.
"However Mr Philippot has repeatedly and publicly implied a link between these terrorist acts and the State of Qatar, affecting the reputation of Qatar and all its citizens.
"The State of Qatar therefore has no choice but to defend its name in the French courts."
Legal papers have been filed in the western Paris suburb of Nanterre, lawyers told AFP.
The papers were filed in early April but only now has the case become publicly known.
Qatar's statement confirming legal action was dated May 30.
In the days after the January 7 gun attack on the satirical Paris magazine Charlie Hebdo which left 12 people dead, Philippot criticised Qatar -- and Saudi Arabia -- in the French media, saying: "These countries finance Islamism which kills".
In response to the suit, a defiant Philippot, 33, who was the National Front's strategic director for leader Marine Le Pen's 2011 presidential campaign, told French TV station BFMTV, that "this is a very serious matter" and "called on all democrats" to support him.
He also tweeted on Monday: "Qatar will not silence me. An Islamist dictatorship will not dictate to the French what they have the right to say."