House ethics leaders Monday publicly rejected Rep. Jeff Flake’s (R-Ariz.) ongoing attempts to force their committee to release details of its investigation into Members’ interactions with the now-defunct PMA Group lobbying firm.

In a statement to the House, Chairwoman Zoe Lofgren (D-Calif.) announced the panel will not act on any of four resolutions referred by the House in recent weeks.

“As in other investigations, although the Committee has discussed in general terms the scope of its investigation, it did not address more specific details of various investigative steps taken by the Committee. To do so would compromise the investigative capabilities of the Committee in this and future matters by chilling voluntary cooperation,” Lofgren said, in a statement released by the committee. “Requiring the disclosure of the details of any investigative body’s activities would damage its ability to conduct its activities. Ethics investigations, in particular, rely not only upon subpoenas, but upon voluntary cooperation.”

Flake’s resolutions aimed to force the Committee on Standards of Official Conduct, commonly known as the ethics committee, to report how many people it interviewed, how many subpoenas it issued and how many documents it reviewed in the PMA investigation.

The ethics committee issued a report in February declaring that no Member of the House and no House staffer had acted inappropriately in providing earmarks to companies that had hired PMA to lobby on their behalf. Roll Call reported in March that it is not clear that the ethics committee actually interviewed any Members or contacted any of the companies involved.

In her statement, Lofgren cited the Office of Congressional Ethics, which initiated an inquiry against seven lawmakers and ultimately recommended further investigation into two of them, suggesting there was evidence of a link between the earmarks provided by those Members and campaign contributions made by the companies. The OCE recommended dismissal of the other five cases.

Lofgren also emphasized that the ethics committee’s decision to dismiss all of the cases does not preclude additional investigation “should new information warranting action become available.”

“Moreover, disclosing specific investigative steps taken in the PMA matter could compromise any ongoing criminal investigations; harm the ability of the Committee to investigate any additional allegations of wrongdoing in this or related matters; discourage those who might bring credible allegations to the Committee in the future from doing so; and chill the voluntary cooperation of those called before the Committee in various investigations,” Lofgren said.

The Justice Department is also investigating PMA, which closed its doors after an FBI raid in November 2008.

Lofgren defended the panel’s investigative work Monday.

“In reaching its unanimous conclusion, the Committee relied not only on the findings provided by OCE, but its own investigation,” Lofgren said. “During the course of its investigation in this matter, the Committee’s staff reviewed close to one-quarter of a million pages of documents. The Committee investigation covered more than 40 companies with ties to PMA. OCE’s findings included interviews with five Members’ offices. The Committee investigation included interviews with 32 Members’ offices. The Committee investigation involved interviews with chiefs of staff, military legislative aides, other Members’ staff, and Appropriations Committee staff. In reaching its conclusions, the Committee relied on the totality of this large magnitude of information.”