PricewaterhouseCoopers LLC and Deloite & Touche LLP had a ring side seat to the collapse of Freddie Mac (NYSE:FRE) and Fannie Mae (NYSE: FNM) which may cost taxpayers hundreds of billions of dollars. The two auditing firms have some serious explaining to do to taxpayers and members of Congress.

According to the New York Times, advisers to the U.S. Treasury Department found that Freddie's accounting methods overstated its financial cushion.

"The company had made decisions that, while not necessarily in violation of accounting rules, had the effect of overstating the firm's capital resources and financial stability," the paper said. "Indeed, one person briefed on the company's finances said Freddie Mac had made accounting decisions that pushed losses into the future and postponed a capital shortfall until the fourth quarter of this yearwhich would not need to be disclosed until early 2009." Fannie Mae used the same methods, though, apparently not as aggressively as Freddie Mac.

A spokesman for Freddie Mac's auditors, Pricewaterhouse, did not immediately return an email seeking comment. In its letter to shareholders filed with the 2007 annual report report, PwC noted that Freddie Mac had changed some accounting policies. It elected to offset the amounts of some derivative contracts as of October 1; elected to measure newly acquired interests in securitized financial assets that contain embedded derivatives at fair value as of January 1, 2007; changed its method for accounting for uncertainty in income taxes as of January 1; changed the method for accounting for defined benefits plans as of December 31, 2006, changed its method for determining gains and losses on sales of certain guaranteed securities as of October 1, 2005

That's quite a bit to keep track of, no? I am sure Congressional investigators will want more detail about why these policies were changed.

Fannie Mae, whose former chief executive Franklin Raines was ousted in 2004 following another accounting scandal, paid Deloitte $49.3 million in fees in 2007. The firm was hired by Fannie Mae in 2005 because its predecessor KPMG missed accounting errors that cost the housing finance company $9 billion in previously reported profit. A Deloitte spokesman declined to comment.

Chief Executive Daniel Mudd told investors following weaker-than-expected first quarter results that this year and next year would beg "tough." Little did he know that those words would foreshadow his ouster along with his counterpart at Freddie Mac Richard Syron. They no doubt will be getting a pretty fat golden parachutte. Both companies have lost a combined $14 billion over the past year.

If the auditors were not as diligent with Freddie and Fannie as they should have been, then members of Congress needs to hold them accountable. The shareholders who have been wiped out by the government's rescue deserve to know if auditors missed signs of the collapse that they should have caught.