WASHINGTON (REUTERS) - The "Fifty Shades of Grey" series of erotic novels are the favourite reading material among former CIA captives held at the Guantanamo detention camp, the Huffington Post quoted a U.S. congressman as saying.

Democratic Representative Jim Moran of Virginia was among congressional delegates who last week toured Camp 7, the top-security facility that holds more than a dozen "high-value" prisoners, including five men charged with plotting the Sept. 11 attacks on the United States in 2001.

"Rather than the Koran, the book that is requested most by the (detainees) is 'Fifty Shades of Grey.' They've read the entire series in English, but we were willing to translate it,"the Huffington Post quoted Mr Moran as saying on Monday.

"I guess there's not much going on, these guys are going nowhere, so what the hell." Mr Moran, who favours shutting down the detention camp on the Guantanamo Bay U.S. Naval Base in Cuba, said he learned about the book's popularity while touring Camp 7 with the base commander and deputy base commander, the head medical official and the officer in charge of that camp.

Mr Moran's office did not return a call from Reuters. A military spokesman said he could not discuss details of Camp 7, whose inmates were held in secret CIA prisons before being sent to Guantanamo in 2006.

"We don't discuss our high-value detainees except in the most generic terms. Further, we do not discuss the assertions made by members of Congress," said Lieutenant Colonel Samuel House, a spokesman for the prison camp.

Some prisoners are taking part in a hunger strike to protest their indefinite detention.

Journalists are not allowed to visit that part of the detention camp but can tour the other prisons and the library that provides books, magazines and DVDs to all 166 captives.

During a visit last week, Reuters saw an eclectic mix of books in numerous languages, from religious tomes to Star Trek novelisations, Agatha Christie mysteries, stress reduction workbooks and the Greek classic "The Odyssey."

Also on offer is "The Hunger Games," according to a librarian who goes by the nickname Zorro."We have the movie and the book too," he said.

Guantanamo librarians have said in the past that they screen reading material for sexual content, even blacking out photos of scantily clad women in the advertisements in sports magazines.