WASHINGTON — The Treasury Department said Monday another large investment company has raised sufficient capital to join the government in buying toxic bank assets to help spur more normal lending.

Marathon Asset Management LP, which was founded by Bruce Richards and Louis Hanover in 1998, raised the $500 million minimum to begin operations. It was the eighth investment group to qualify for the program.

With the addition of New York-based Marathon, the selected companies have raised $5.07 billion which the Treasury Department has matched dollar for dollar, using resources from the $700 billion financial bailout program.

Besides the $10.13 billion in total equity capital, Treasury has provided the same amount in debt capital, boosting the total purchasing power of the program to $20.26 billion, the department said Monday.

Treasury also said it soon expects to announce a final company has qualified to participate in the Public-Private Investment Program, or PPIP, which has been plagued by delays while analysts continue to doubt how successful it will be in buying banks’ bad assets.

The Obama administration, however, maintains that the effort will draw private capital into the effort to purchase banks’ toxic assets, which keeps taxpayers from shouldering the entire burden of the program.

Treasury had announced in July that nine investment groups had qualified to participate in the PPIP program with each group being given time to raise the initial $500 million needed to begin operations.

Congress approved the $700 billion bailout program in October 2008 in an effort initially designed by the Bush administration to focus primarily on buying bad assets from banks. That goal shifted almost immediately to direct injections of capital into banks after then-Treasury Secretary Henry Paulson decided that amid a rapidly worsening financial crisis, it would take too long to get the toxic asset program up and running.