A trust overseeing the bankruptcy of Taylor, Bean & Whitaker Mortgage Corp, or TBW, and one of the company's subsidiaries filed complaints in a Miami Circuit Court claiming a combined $7.6 billion in losses.
Deloitte "certified TBW as a solvent, viable company with accurate financial statements every year from 2001 to 2008," one of the complaints said.
"Despite Deloitte's credentials and expertise as one of the 'Big 4' accounting firms, those statements -- and the rosy picture they depicted of TBW -- were completely false," it said.
Deloitte spokesman Jonathan Gandal said the "claims are utterly without merit."
It was the latest lawsuit to hit one of the major accounting firms over their role in the credit crisis.
Pricewaterhouse Coopers, KPMG and Ernst & Young are also facing accusations about their auditing standards by investors who collectively seek to recoup billions of dollars lost in the financial meltdown.
Lee Farkas, the former chairman of Taylor, Bean and Whitaker, was sentenced to 30 years in prison in April for masterminding what U.S. officials described as one of the biggest bank frauds ever.
U.S. Justice Department officials said Farkas ran a $2.9 billion fraud scheme that led to TBW's downfall and the collapse of one of the largest U.S. regional banks, Colonial Bank.
The complaint filed by Neil F. Luria, a plan trustee of Taylor, Bean & Whitaker Trust, claims losses of approximately $6 billion. A second complaint by Ocala Funding, a wholly owned TBW subsidiary which served as a lending facility, claims losses of $1.6 billion.
Farkas was accused of running a wide-ranging scheme to cover up large losses at Taylor, Bean, which was based in Ocala, Florida, by moving funds between accounts at Colonial Bank and also by selling mortgage loans that either did not exist, were worthless or had already been sold.