"The terrorist attacks on September 11 were both immoral and counterproductive."
Sayyid Imam al-Sharif, who goes by the nom de guerre Dr Fadl, helped bin Laden create al-Qaeda and then led an Islamist insurgency in Egypt in the 1990s.
In a book written from inside an Egyptian prison, he launched a frontal attack on al-Qaeda's ideology and the failings of bin Laden and his deputy, Ayman al-Zawahiri.
"Every drop of blood that was shed or is being shed in Afghanistan and Iraq is the responsibility of bin Laden and Zawahiri and their followers," writes Dr Fadl.
"The terrorist attacks on September 11 were both immoral and counterproductive, he writes. "Ramming America has become the shortest road to fame and leadership among the Arabs and Muslims. But what good is it if you destroy one of your enemy's buildings, and he destroys one of your countries? What good is it if you kill one of his people, and he kills a thousand of yours?" asks Dr Fadl. "That, in short, is my evaluation of 9/11."
He goes on to write about Muslims who move to the West and then take up terrorism.
"If they gave you permission to enter their homes and live with them, and if they gave you security for yourself and your money, and if they gave you the opportunity to work or study, or they granted you political asylum," writes Dr Fadl, then it is "not honorable" to "betray them, through killing and destruction" .
Dr Fadl focuses his attack on Zawahiri, a key figure in al-Qaeda's leadership and a fellow Egyptian who he has known for 40 years. Zawahiri is a "liar" who was paid by Sudan's intelligence service to organise terrorist attacks in Egypt in the 1990s, he writes.
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