Angry proponents of piggybacking say they'll organize a grass-roots campaign to fight against the change.
With piggybacking, a consumer with poor credit is placed as authorized user on the credit card of a person with a stellar credit history. Authorized users benefit from having the payment history of the primary cardholders show up on their credit reports, thereby improving their credit scores.
Lenders have complained that it is fraud and distorts the credit score system.
Internet companies have created an industry by playing middleman -- paying a small sum to those with good credit to take on those with bad credit as authorized users, then collecting healthy fees from those consumers.
Now one of those Web-based firms has threatened to organize an effort to expose problems in the credit scoring system.
"Our very existence (proves) that the FICO system is so flawed," says John Coates, spokesman for Instant Credit Builders based in Largo, Fla.
Fair Isaac says that starting in September it will ignore authorized users as it calculates the renowned FICO credit score.
"Fair Isaac has become aware that Web-based services are using authorized trade lines to defraud lenders," says Craig Watts, spokesman for Fair Isaac. "While we work with the financial services industry on an industry solution, we wanted to protect lenders and FICO scores."
The FICO credit score is used by lenders to assess risk in lending money. Lenders factor this number, which can range from 300 to 850, in credit decisions. Watts says 90 percent of the largest U.S. banks base their loan decisions on FICO credit scores.
Watts says the change will prevent people from misleading lenders about their true credit risk.
Coates argues the system can't be easily changed.
"Maybe our system can definitely show you, OK, there seems like there's a loophole and there are flaws that increase the score. You know what? There are also a zillion flaws that decrease the people's scores."
He says Instant Credit Builders plans to bring to light every flaw in the credit scoring system.
"We are building a community of people that are going to stand up. We will petition against it and we are actually going to formulate plans to work together as a grassroots effort to actually create a financial revolution," he says.
Those who rent credit histories won't be the only ones suffering a loss. Often parents will attempt to give their children a jump-start on a good or improved credit history, and they'll be taking a hit as well.
