Fraudulent practices and false representations made by units at Countrywide Financial Corp. led MBIA Insurance Corp. to guarantee mortgage-backed securities that have already cost the insurer $459 million in policy claims and exposed it to several hundred millions more, MBIA said in a lawsuit filed earlier this week.

Anxious to expand its market share, Countrywide engaged in "a wide variety of deceptive practices" and "deliberately abandoned its own guidelines to drive up revenues from increased originations fees, securitization fees, and servicing fees — no matter the cost to borrowers, investors, or guarantors like MBIA," according to the suit filed in New York Supreme Court. Bank of America Corp. — which acquired Countrywide earlier this year — declined to comment on the lawsuit. It has 30 days to respond to the complaint in person or 35 days by mail, the court clerk's office said.

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