PARIS (Reuters) - France's far right National Front will sue Madonna after she screened footage of party leader Marine Le Pen with a swastika superimposed on her face at a concert in Paris on Saturday, a party official said.

The video shown on a huge screen has already been used on other legs of the U.S. singer's tour and shows the singer's face merging with other public figures, such as Pope Benedict and former Egyptian President Hosni Mubarak, who was toppled by popular protests last year.

The face of the National Front leader appears for a few seconds, with the Fascist symbol briefly imposed on it, and is followed by the features of a man resembling Adolf Hitler.

"A private plaintiff's case for insult will be presented next week," Florian Philippot, vice-president of the National Front, told Reuters.

He called the images an "unacceptable" provocation for attempting to associate Le Pen, who won 18 percent of the vote in April's first-round presidential election in France, with fascism.

Since taking the reins of the National Front last year from her ex-paratrooper father Jean-Marie, Le Pen has tried to widen her party's appeal by expelling extremists and cracking down on racist talk and anti-Semitism.

"It is our duty to bring a complaint to defend our voters and our supporters," Philippot said.

Although Le Pen's calls for protectionism and for France's to exit the euro currency have won sympathy with some parts of the electorate, the party won only two seats in the 577-member National Assembly in last month's legislative elections, partly due to France's first-past-the-post electoral system.

(Reporting by Patrick Vignal; Editing by Alison Williams)