The Treasury Department paid out more than $27 million to law firms overseeing the financial bailouts without requiring detailed bills or questioning the incomplete records that the lawyers provided, a government watchdog says.

Treasury's "current contracts and fee bill review practices create an unacceptable risk that Treasury, and therefore the American taxpayer, is overpaying for legal services," the Special Inspector General for the Troubled Asset Relief Program said in a report issued Thursday.

Treasury could not have adequately gauged whether the fees were reasonable because the records are so sparse, the report says.

The report criticizes so-called "block billing," in which law firms submit "vague and inadequate descriptions of work, and administrative charges — all of which should have been questioned before payment," the report says.

Treasury staff failed to question the charges for work that was described vaguely, the report says.