More than 100 used car dealers, including 11 on Long Island, have sued Carfax, claiming that the provider of heavily advertised vehicle history reports is violating federal antitrust laws by excluding competition.

The suit says that the near absence of competition results in higher prices for dealers, who furnish the reports to car shoppers, and for consumers who purchase the reports on their own, while discouraging sales of what the suit says are more reliable competing reports.