WASHINGTON  One of Al Qaeda's senior theologians is calling on his followers to end their military jihad and saying the attacks of September 11, 2001, were a "catastrophe for all Muslims."

In a serialized manifesto written from prison in Egypt, Sayyed Imam al-Sharif is blasting Osama bin Laden for deceiving the Taliban leader, Mullah Omar, and for insulting the Prophet Muhammad by comparing the September 11 attacks to the early raids of the Ansar warriors. The lapsed jihadist even calls for the formation of a special Islamic court to try Osama bin Laden and his old comrade Ayman al-Zawahri.

The disclosures from Mr. Sharif, also known as Dr. Fadl and Abd al-Qadir ibn Abd al-Aziz, have already opened a rift at the highest levels of Al Qaeda. The group's deputy, Ayman al-Zawahri, a former associate of the defecting theologian in Egypt, personally mocked him last month in a video, remarking that he was unaware Egyptian prisons had fax machines. Meanwhile, leading Western analysts are saying the defection of Mr. Sharif indicates the beginning of the end for Al Qaeda.

The author of "Inside Al Qaeda," Rohan Gunaratna said in an interview this week, "There is nothing more important than a former jihadist as important as Dr. Fadl criticizing the jihadist vanguard." Mr. Gunaratna, who acts at times as a consultant for American and Western intelligence, described the reformed theologian as "both an ideologue and operational leader, but he was primarily an ideologue."

An expert on Islamic terrorism with the Jamestown Foundation, Steven Ulph, also said the defection of Mr. Sharif could hemorrhage support for Al Qaeda. "The important point to make, when you have the combination of a respected ideologue, plus someone who was in the field, say these things it is more important than having a Saudi sheik that moderates his message," he said.

The director of the Homeland Security Policy Institute at George Washington University, Frank Cilluffo, said, "Here you have someone with the stature and credibility, who more or less wrote the book on jihadism and is oft cited by other jihadists, making the case against it. This is someone with the heft on legal and religious grounds to make the counter argument that we can't."

Mr. Sharif, currently serving a life sentence in an undisclosed Egyptian prison, wrote in the 1980s two of the modern seminal texts for Sunni jihadism and in particular Al Qaeda, in "Fundamental Concepts Regarding Jihad" and "The Five Ground Rules for the Achieving of Victory or Its Absence." Those books are scholarly justifications, citing the Koran and Hadiths, for joining a war against Muslim apostates such as the Egyptian ruling class and for a broader jihad against the far enemy of America.

Originally rounded up in the arrests following the 1981 assassination of Egyptian president, Anwar Sadat, Mr. Sharif served in an Egyptian jail with Ayman al-Zawahri, who would later go on to be the deputy to Mr. bin Laden. In 2001, shortly after the September 11 attacks, Mr. Sharif was arrested in Yemen and was later sent to Egypt in 2003 or 2004.

His latest texts are a renunciation of his earlier work, saying the military jihad or war against apostate states and America is futile. But the ex-jihadist also calls into question the virtue of Mr. bin Laden and Mr. Zawahri. In some ways the manifesto reads in parts like a spicy Washington memoir by an embittered former official.

Of his old associates he writes, "Bin Laden, al-Zawahri, and others fled at the beginning of the American bombing [in Afghanistan], to the point of abandoning their wives and families to be killed along with other innocent people," according to a translation provided by the Middle East Media Research Institute. It goes on, "I think that a sharia court should be established, composed of reliable scholars, to hold these people accountable for their crimes  even if in absentia  so that those who are ignorant in their religion do not repeat this futility."

Mr. Sharif also says Mr. Zawahri informed on his friends after he was arrested following the Sadat assassination in 1981. "I don't know of anyone in Islamic history having committed such deceit, fraud, falsification, and betrayal of trust with such hostility to someone else's book, and perverted it - no one before Ayman al-Zawahri," he wrote.

Last month, in a video produced by Al Qaeda's production company, Mr. Zawahri said the latest recantations from his one time friend were the result of torture, asking if the electrical current for the fax machine he used to serialize his new book in the Arabic press also powered the prison's electric chair. Egypt has been singled out by Human Rights Watch and other human rights groups for the practice of torture in its prisons, particularly the use of electric shocks. In February, a man named Abu Omar who claimed to be kidnapped by the CIA and transported to an Egyptian prison described in detail how he was tortured during his interrogations by Egypt's security services.

On Monday, an American intelligence official familiar with the interrogation of Mr. Sharif said that in 2004 the Al Qaeda cleric was tortured. "All I am saying is that screw drivers were involved," this official, who asked to be anonymous, said. When asked if Mr. Sharif was tortured, Mr. Gunaratna responded by saying, "He spent time in an Egyptian prison."

But Mr. Gunaratna also said he believed Mr. Sharif's conversion was genuine. "He has had a genuine change of heart because we are seeing a trend today in Egypt where the original members of both of the major jihadist organizations are turning, the senior members of these groups, many have gone back and been remorseful," he said. "He is not an exception because there is a trend. . . The traditional jihad movement is almost coming to an end. What has it accomplished in more than 25 years?"

Two spokesmen for American government agencies yesterday declined to comment on this story.