05/05/2014 05:34 pm ET Updated May 06, 2014

Media Matters' David Brock Urges CBS News To Reopen '60 Minutes' Benghazi Investigation

NEW YORK -- Media Matters chairman David Brock is urging top CBS News executives to reopen the network's internal investigation over its discredited "60 Minutes" report on the Benghazi attack.

Lara Logan, the network's chief foreign correspondent, and Max McClellan, her producer, went on leave following the network's internal review and have not returned. A New York magazine report, published Sunday night, has renewed interest in the network controversy and provided new details about how the erroneous Oct. 27 story -- which featured a discredited "eyewitness" and several unsourced claims about the September 2012 attack that killed four Americans -- ever made it on air.

Brock, who founded the progressive media watchdog, addressed Monday's letter to CBS News chairman and "60 Minutes" executive producer Jeff Fager and CBS News president David Rhodes. In the letter, he wrote that the New York magazine story "raises critical questions about the validity of CBS' investigation."

"Re-opening the investigation is warranted as it now appears that CBS' internal investigation was not thorough, was wrong on critical points, and omitted key facts -- facts that would have revealed that Logan's report was tainted by partisanship and unprofessional conduct," Brock wrote.

Specifically, Brock noted that the internal review said Logan had reached out to security firm Blue Mountain, the State Department and the FBI regarding Dylan Davies, the security contractor who claimed to have witnessed the attack but was later revealed to have told his employer and the FBI that he did not reach the compound that night. New York magazine's Joe Hagan reported that Logan did not contact the State Department or FBI.

Brock also wrote that CBS' review did not disclose that Logan consulted with Sen. Lindsey Graham (R-S.C.), one of administration's toughest critics on Benghazi, while preparing the story. The morning after Logan's "60 Minutes" report aired, Graham seized upon Davies' bogus account as evidence that all the Benghazi survivors had not been heard from and that Obama administration appointees should be blocked until all witnesses had testified before Congress.

"Did CBS know how closely Logan was collaborating with Sen. Graham on the Benghazi report?" Brock asked. "If so, why was this not disclosed on air or in CBS' review of the erroneous report?"

In the letter, Brock also raised questions about reported restrictions placed on other CBS reporters while Logan pursued the Benghazi story, as well as questions about the vetting process prior to its broadcast.

Brock, a right-wing Clinton antagonist in the 1990s, turned left and went on to found Media Matters and super PAC American Bridge. He recently started Correct the Record, a new initiative to defend Hillary Clinton, who was secretary of State at the time of the Benghazi attack. In October, Brock wrote "The Benghazi Hoax," an e-book examining how Republicans and conservative media have promoted what he considers a "phony scandal."

Media Matters comprehensively covered inconsistencies in Davies' account of the night of the attack, and Brock called upon Fager and Rhodes to retract the story on Nov. 1.

But CBS did not retract it, and went on to ignore or sidestep HuffPost's questions about the conflicting accounts for nearly a week. The "60 Minutes" report completely unraveled on Nov. 7, with Logan apologizing on air the next morning.

In Monday's letter, Brock reiterated his previous call for CBS to conduct an independent investigation, similar to the one that followed Dan Rather's 2004 report on George W. Bush's military service with the Texas Air National Guard. The independent committee produced a 224-page report, and as a result CBS ousted four employees. Rather, his role diminished, left the network in 2006.

"As long as these discrepancies and questions remain unaddressed and until full accountability is taken, it is impossible for that to happen," Brock wrote, adding that he hopes the executives "take this opportunity to reassure your viewers of CBS' standards and accountability."

A "60 Minutes" spokesperson did not immediately return a request for comment.

Read the full letter here:

David Brock Letter