Still simmering tensions between the FBI and the CIA over the September 2001 terrorist attacks and their aftermath have been reignited by a row over a forthcoming book by a former FBI agent that is strongly critical of the main US foreign intelligence agency.

The Black Banners: The Inside Story of 9/11 and the War Against Al-Qa'ida,is written by Ali Soufan, who was involved in many major terror investigations between 1997 and 2005.

But its first edition seems likely to be scarred by dozens of cuts demanded by the CIA – according to insiders who have seen the memoir, less for national security reasons than out of a desire to avoid re-airing incidents that show

the Agency in an unflattering light. The excisions were "ridiculous," Mr Soufan told The New York Times yesterday.

Two issues, both of them publicly well documented, are at the centre of the dispute. One is the failure of the CIA in 2000 to inform the FBI of the presence of two al-Qa'ida suspects who later took flying lessons to prepare for their role in the 9/11 attacks. Some details of the episode, which reflected the dismal relations between the two agencies at the time, have been redacted, although they were detailed in the official 9/11 Commission report, issued in 2004.

The book also removes all first person references in an account of a CIA interrogation session that Mr Soufan witnessed and described as unnecessary and counterproductive, seemingly in an effort to dilute the impact of an account of what critics maintain was torture.