"Classification of information is designed to protect the national security of the United States, not to be used as a shield to protect the government from embarrassment."

So wrote US Senator Sheldon Whitehouse in a September 25, 2008 letter [pdf below] to then-Director of National Intelligence Mike McConnell expressing frustration over the CIA's refusal to declassify four written passages — located in an unknown document that may still be classified — related to the agency's destruction of interrogation videotapes.

"The CIA has asserted that the text that I have identified 'constitutes vital lines of unguarded internal communication between our personnel deployed to the field and headquarters,'" wrote Whitehouse, formerly a member of the Senate Intelligence Committee. "While I understand this answer, it does not constitute a basis for classifying or refusing to declassify information under the relevant executive order. Nor does this implicate 'sources and methods.' This information does not damage national security — that damage was done when the CIA embarked on an interrogation program that included waterboarding."

It was the purge of the videotapes — one of which depicted the waterboarding of accused terrorist Abu Zubaydah — ordered by top CIA official Jose Rodriguez, along with a subsequent cover-up alleged by lawmakers, that was the catalyst behind the Senate Intelligence Committee's five-year-long investigation into the CIA's detention and interrogation program. The Senate probe was launched six months after Whitehouse sought declassification of the four passages.

Whitehouse's letter was recently declassified and is one of several documents about the videotapes' destruction obtained by VICE News through a Freedom of Information Act (FOIA) request after a four-year wait. The Democratic senator from Rhode Island was not only upset at then-CIA Director Michael Hayden's refusal to declassify the four passages about the videotapes' destruction, he was outraged that the CIA had classified Hayden's response to him as "SECRET/NOFORN," which means the information is secret and cannot be shared with foreign nationals. That meant that Whitehouse's letter of complaint to McConnell articulating specific points contained in the letter from Hayden also had to be classified.

"I have had to send this letter in classified form to quote to you from that [Hayden] letter — the absurdity is self-evident," Whitehouse wrote. "I would welcome a precise explanation as to what information in the CIA letter is classified and why."

Hayden is one of a handful of former CIA officials who was publicly critical of the findings and conclusions in the Intelligence Committee's torture report. He helped launch the website CIASavedLives.com as a vehicle to present the public with "documents that conclusively demonstrate that the [detention and interrogation] program was: authorized by the President, overseen by the National Security Council, and deemed legal by the Attorney General of the United States on multiple occasions."

Whitehouse's letter provides new insight into what later became a very public and a very lengthy battle between the Senate Intelligence Committee and the CIA over what could and could not be declassified in the torture report. The Intelligence Committee finally released a declassified executive summary of its mammoth 6,700-page report last December after months of negotiations with the CIA and the White House.

Steven Aftergood, the director of the independent Project on Government Secrecy, said the letter underscores that the Senate Intelligence Committee "was clearly on notice early on that classification disputes were going to be a problem in the review of CIA interrogation practices.

"In retrospect, the Committee should have confronted this issue sooner, and more directly," he told VICE News. "Simply pointing out the absurdity isn't enough to eliminate it. In fact, in the clash of wills between the CIA and Senator Whitehouse, it appears that the CIA won out."

The CIA's reply to Whitehouse, Aftergood added, makes clear that the agency "is taking a very expansive view of the scope of national security classification. For the agency, it includes not only intelligence sources and methods but also the sort of material that would be withheld under FOIA as 'deliberative' information. This leads to absurd consequences, as Senator Whitehouse pointed out, such as the classification of his own letter."

Whitehouse threatened to have the Intelligence Committee refer the issue directly to the Public Interest Declassification Board if McConnell refused to address the matter, which would have been an unprecedented move. Congress established the board in 2000 "to promote the fullest possible public access to a thorough, accurate, and reliable documentary record of significant US national security decisions and activities."

There's no indication, however, that Whitehouse ever approached the Declassification Board. The CIA declined to comment for this story.

Whitehouse's office and staffers for several key members of the Intelligence Committee told VICE News that they can't recall what the four passages about the destruction of the videotape actually said. On Monday, Whitehouse's staffers were still trying to track down what he had requested the CIA to declassify and why.

Most of those passages remain secret, according to an official familiar with the contents of the Senate's still-classified 6,700-page report, who spoke on condition of anonymity in order to discuss what is still a sensitive issue. (Whitehouse was a member of the Intelligence Committee from 2007 until 2011 and was deeply involved in the early stages of compiling the torture report.)

That said, the executive summary of the Senate torture report contains about two dozen references to the CIA's destruction of the videotapes and discussion about what was depicted on it.

"Here's the rub," the official said. "I also am told that some of the passages may be in the summary, but can't relay which ones."

Follow Jason Leopold on Twitter: @JasonLeopold