With more people falling behind on their consumer loan payments, regulators and consumer advocates say they're seeing a surge in aggressive — and sometimes questionable — debt-collection tactics.

Complaints against debt collectors, after plunging in 2005, are rising again, the Council of Better Business Bureaus said. Complaints surged 20 percent in 2006 and 26 percent in 2007, according to the BBB's preliminary figures. And the Federal Trade Commission, which receives more complaints about debt collectors than about any other industry, said it's seen a steady rise in complaints against debt collectors.

Even in the best of times, debt collectors can be aggressive in collecting on delinquent loans. But as the economy slumps, collectors are filing more lawsuits to recoup debt and calling consumers who can't pay their bills more quickly and more often, according to consumer groups and collectors.

Jerry Jarzombek, a lawyer in Fort Worth, who represents debtors, said he's also seeing more people who fall behind on their bills "threatened, because it's harder to get someone to pay when they don't have extra dollars."

He added, "I see more and more things put in writing that are false, in an attempt to collect the debt."

Gary Wood, past president of DBA International, a trade group for debt collectors, said, "There have always been agencies that have been extremely aggressive," but we're "trying to clean (those agencies) out of our association."

Federal law bars debt collectors from repeatedly calling borrowers after being asked, in writing, to stop and from threatening people with fake lawsuits. Some regulators say that as the economy struggles, they're seeing more violations of the law by debt collectors.

A glimpse of what's happening across the U.S.:

In New York, Attorney General Andrew Cuomo has fined two debt-collection agencies over the past six months for falsely pretending to be lawyers, among other tactics.

The California attorney general is receiving more complaints against debt collectors and has begun investigating "a couple" of collection agencies, said Al Shelden, head of the office's consumer law section.

In Minnesota, Attorney General Lori Swanson said she plans to file lawsuits against debt collectors for increasingly "abusive" tactics. Her office is receiving more complaints about collectors, trying to collect debt from the wrong person and garnishing Social Security benefits in violation of state law.