Grassley has asked the SEC to respond to these allegations, which he says were made by an agency whistle-blower decribing "the SEC’s unlawful destruction of the federal records generated in at least 9,000 informal investigations."

The allegedly destroyed documents are said to pertain to "matters under inquiry," or MUIs. That's the official term used by the SEC for the preliminary stages of an investigation. MUIs may or may not turn into official investigations.

After reviewing the whistleblower’s letter and supporting documents, Grassley sent a letter to SEC chairman Mary Schapiro.

"If (the whistleblower’s) allegations are correct, the intentional destruction of at least 9,000 MUIs would appear to greatly handicap the SEC’s ability to create patterns in complex cases and calls into question the SEC’s ability to properly retain and catalog documents," the letter said.

Grassley is requesting a "full accounting" of the SEC's document destruction policies, including whether the allegations are correct that the SEC destroyed documents related to Bernard Madoff, Goldman Sachs, Wells Fargo, Bank of America, Deutsche Bank, Lehman Brothers, and SAC Capital.

Questions? Comments? Email us atNetNet@cnbc.com

Follow John on Twitter @ twitter.com/Carney

Follow NetNet on Twitter @ twitter.com/CNBCnetnet

Facebook us @ www.facebook.com/NetNetCNBC