SAN DIEGO -- Four travel agencies, along with a former travel agency owner, have filed a class-action suit against six major car rental systems, alleging that the RACs have routinely short-changed travel agents on commissions since 1999.

The lawsuit, filed June 12, names Avis, Budget, Dollar, Thrifty, Enterprise and Hertz as defendants.

The travel agencies behind the suit are Wide World Tours of Mission Valley, based in California; Travel Support Systems, which operates as Outside Sales Support Network in Florida; Vacation Marketing Group of Hawaii, and International Travel Bureau in California. Cecilia Pedroza, who recently folded her own travel agency, is also a plaintiff.

The lawsuit alleges that the rental companies violated their own commission agreements by failing to include all revenue sources when calculating travel agency commissions. Revenue sources unjustly excluded from commissions have included airport concession recovery fees, vehicle upgrades, collision damage waiver and supplemental liability insurance sales, additional driver fees, fees for drivers under 25, and refueling charges, said Alexander Anolik, one of the attorneys representing the travel agents.

In addition, Anolik said, rental companies have begun deducting processing fees from commission checks issued to travel agents. "They're charging the agents to get their own commission," he said.

"The lawsuit has no merit, and we will oppose it vigorously," said Ted Deutsch, vice president of communications and public affairs for Cendant Car Rental Group, which operates Avis and Budget.