LOS ANGELES, JULY 5 -- Two of the nation's best known credit card companies said today that they have filed a joint lawsuit accusing a telemarketing operation of engaging in a massive international fraud scheme by "laundering" credit card receipts.

Visa International Service Association and MasterCard International Inc. allege in the lawsuit that individuals and telemarketing firms in several states violated federal racketeering and copyright laws through their operation of the scheme.

"It is one of the largest operations that we've seen," said David Brancoli, a spokesman for Visa USA Inc. in San Francisco. "We estimate that it has already caused approximately $50 million in fraudulent credit card sales drafts to have been laundered."

Of those, he said, the credit card companies have documented $4 million in losses so far.

The suit, filed in U.S. District Court in Los Angeles, marks the latest action by the two companies against credit card launderers, telemarketers or others who contract with legitimate businesses to handle their credit card receipts. The credit card industry contends that disreputable firms collect on the receipts and then skip town, leaving banks liable when the receipts prove uncollectable.

Visa and MasterCard estimate that they incur $160 million to $200 million a year in losses from unscrupulous telemarketers, of which about 75 percent is due to laundering. "There's no question about it ... when we find it, we go after it," Brancoli said.

The latest suit asks the court to immediately halt the allegedly fraudulent sales practices of Donald E. Gaines of Florida and nine other people, some of whom purportedly operated a series of telephone sales operations with names like Telstar Marketing Network Inc. and MW1 Marketing in Arlington, Texas. None could be reached for comment.

Brancoli said that their operations reached into Puerto Rico and Canada, besides states from coast to coast.

The telemarketers, according to the lawsuit, operated "boiler room" telephone operations to hawk products ranging from vitamins to home security systems. Unscrupulous telemarketers typically entice potential customers to give them their credit card numbers, then submit credit card orders under those customers' names, even though the customers did not order any merchandise.

Such telemarketers are deemed ineligible to handle Visa or MasterCard, the suit states. Accordingly, they advertise in newspapers to find companies willing to handle, or "launder," their credit card receipts in return for a commission, typically about 6 percent. That way, the telemarketers can exchange their credit card receipts for cash.

If the telemarketers are able to collect on their receipts for goods that were never ordered by a consumer, the launderer's bank is liable for the losses.