But as the bureaus’ work has become more important, consumer advocates say, regulation has not kept up, in large part because their overseer, the Federal Trade Commission, lacks broad authority. That could change once responsibility for the credit bureaus shifts to the new Consumer Financial Protection Bureau, which will be able to write rules and examine the credit agencies’ policies.

The bureaus, meanwhile, do not have an economic incentive to improve the system, consumer advocates say, because their main customers are the creditors, not consumers.

“There is no neutrality in the credit reporting agencies,” said John Ulzheimer, who has been an expert witness in more than 80 credit-related cases and is president of consumer education at SmartCredit.com. “They work for the lenders who buy credit reports from them, and anyone who suggests otherwise is not being intellectually honest.”

When asked about the V.I.P. category, TransUnion said all consumers “have the ability to speak to a live representative.” Equifax said consumers who received a free copy of their credit report were provided with a number for customer service.

Experian denied that it had V.I.P. lists. But a spokeswoman did say that prominent people deemed high risk — like politicians in an election year — might have their credit files taken offline so that creditors or other companies making inquiries could not get access without the bureau’s permission. Experian said those people did not receive any other special handling.

David Szwak, a consumer lawyer in Shreveport, La., who has handled dozens of credit cases, said that the V.I.P. designation and preferential treatment did exist at Experian, and he provided sworn testimony from former Experian employees that the category existed.

Estimates of credit reports with serious errors vary widely, anywhere from 3 to 25 percent. A recent study, paid for by the Consumer Data Industry Association, the trade group for the bureaus, found potential errors in 19.2 percent of reports, but said that less than 1 percent of them had disputes that, when settled, resulted in a meaningful increase in scores. Even 1 percent translates into millions of consumers, since there are at least 200 million files at each of the bureaus.