The complaint filed in courts in Liege in eastern Belgium and in Paris claims that Internet betting companies stain the reputation of the clay-court championship at Roland Garros.

"There is urgency to act because sporting ethic is at risk," Jean-Francois Vilotte, director general of the French tennis federation, told The Associated Press. "It is an issue as important as the fight against doping."

The issue of integrity in tennis came to the fore in August, when an online betting site — Betfair — voided all wagers on a match in Poland between fifth-ranked Nikolay Davydenko and 87th-ranked Martin Vassallo Arguello because of irregular betting patterns. Davydenko withdrew from the match in the third set, citing a foot injury.

The French federation is suing three companies — Betfair, Bwin and Ladbrokes — with a court injunction to stop them from taking bets on the French Open. It seeks a fine of $75,000 a day for any violations, said Vilotte's lawyer, Jean-Louis Dupont.

Dupont said the federation's case is built on two tenets: that the betting companies are tainting the reputation of the French Open and unfairly using the tournament as a way of making money.

If a match-fixing scandal hit the French Open, it would undermine the value of the tournament, which had a 2007 revenue $175 million and attracted 450,000 fans to Roland Garros and a potential 3 billion viewers worldwide, Dupont said.

"Targeting the only betting operator which is completely transparent and, where needed, shares all its betting informtion with the ITF and ATP would be just plain bizarre," Betfair Managing Director Mark Davies wrote in an e-mail. "I would be astonished if any sensible regulator wanted to go down this route or believed it could help protect the integrity of its sport when it so obviously does the opposite."

With soccer and horse racing, tennis is among the most popular sports to bet on.

When Vilotte monitored the ATP Masters Series tournament in Paris, which the French federation also organizes, he said bets over the weeklong event totaled between $750 million and $1.5 billion.

"You can imagine that for Roland Garros, the totals would be much higher," he said.

The federation says the betting companies manage to avoid being stuck with the fallout when there is suspicion of match fixing.

"They purely scrap the bets on the event in question and by doing that generate a scandal that the organization and players have to deal with. It can give them a lifelong ugly reputation," Dupont said.

The ATP opened an investigation into the Davydenko match, interviewing him and his wife and reviewing telephone records. No findings have been announced.

Since the match, several players have come forward to say they have been approached with offers to fix matches.