The top Democrat on the House panel investigating whether the failed mortgage giant Countrywide gave lawmakers preferential treatment blasted committee Chairman Darrell Issa (R-Calif.) today for trying to keep their names quiet.

In a letter to the House Oversight and Government Reform Committee chairman, ranking member Elijah Cummings (Md.) questioned why Issa asked the law firm responding to a subpoena to redact information that could identify current and former lawmakers from the documents it sends the committee.

“You have instructed the law firm responding to your Countrywide subpoena to redact the names and any other information that might identify specific Members of Congress from any additional documents still to be produced to the Committee, including the loan files for two of these four Republican Members: NRCC Chairman [Pete] Sessions and [Elton] Gallegly,” Cummings wrote.

“It is also unclear why you have chosen this point in the investigation to direct the redaction of information that would identify select Members of Congress, particularly since the Committee has already received unredacted documents relating to other Members, including Senator [Chris] Dodd, Senator [Kent] Conrad and Chairman [Buck] McKeon,” he added. “You have not explained why you now want to treat some Members differently than others.”

Issa has for more than three years blasted Countrywide’s “Friends of Angelo” loan program, named for company CEO Angelo Mozilo, as “public corruption” and “bribery.”

At the start of the investigation, two powerful Senate Democratic chairmen — Budget Chairman Kent Conrad (N.D.) and then-Banking Chairman Chris Dodd (Conn.) — were tied to the mortgage giant but cleared by the Senate Ethics Committee in August 2009 because there was “no credible evidence” that they had participated in a program that was not available to the public.

Earlier this month, House Armed Services Chairman Buck McKeon (R-Calif.), retiring Rep. Elton Gallegly (R-Calif.) and National Republican Congressional Committee Chairman Pete Sessions (R-Texas) were identified in news reports as three of the four Members recently implicated in Issa’s probe. The file on McKeon was produced in unredacted form to the committee.

The identity of a fourth individual, described as a former Republican lawmaker, has not yet been uncovered.

Democrats on the oversight panel began asking Issa how he intended to continue with the investigation, given that the Members in question were prominent Republicans whom Issa had not yet identified but who had been referred to the House Ethics Committee.

An Issa spokesman dismissed the suggestion of partisan impropriety today, saying the thrust of Cummings’ letter was “deeply misleading.”

“For Members of Congress, the committee has requested that Bank of America deliver two copies of all files — one unredacted and the other in redacted format. The central assertion in Ranking Member Cummings’ letter is deeply misleading and follows a three year pattern of attempting to obstruct the committee’s efforts to examine the Countrywide VIP program, including the involvement of House and Senate members and staff,” Issa spokesman Frederick Hill said in a statement.