The US's most senior general was "hoodwinked" by top Bush administration officials determined to push through aggressive interrogation techniques for terror suspects held at Guantánamo Bay, the Guardian can reveal.

The development led to the US military abandoning its age-old ban on the cruel and inhumane treatment of prisoners.

General Richard Myers, the chairman of the US joint chiefs of staff from 2001 to 2005, wrongly believed that inmates at Guantánamo and other prisons were protected by the Geneva conventions and from abuse tantamount to torture.

The way he was duped by senior officials in Washington - who believed the Geneva conventions and other traditional safeguards were out of date - is disclosed in a devastating account of their role, extracts from which will be published in tomorrow's Guardian.

In his new book, Torture Team, Philippe Sands QC, a professor of law at University College London, reveals:

 Senior figures in the Bush administration pushed through previously outlawed measures with the help of unqualified and inexperienced military officials at Guantánamo.

 Myers believes he was a victim of "intrigue" by top lawyers at the department of justice, the office of the vice president, Dick Cheney, and Donald Rumsfeld's defence department.

 Myers wrongly believed interrogation techniques had been taken from the army's field manual.

The lawyers who pushed through the interrogation techniques - all of them political appointees - were Alberto Gonzales, David Addingon and William Haynes.

Others involved were Doug Feith, Rumsfeld's undersecretary for policy, and Jay Bybee and John Yoo, two assistant attorney generals.

The revelations have already sparked a fierce response in the US from those familiar with the contents of the book.

They are determined to establish accountability for the way the Bush administration violated international and domestic law by sanctioning prisoner abuse and torture.

The Bush administration has tried to explain away the ill-treatment of detainees at Guantánamo and the Abu Ghraib prison, in Baghdad, by blaming junior officials.

Sands establishes that pressure for the aggressive and cruel treatment of detainees came from the very top and was sanctioned by the most senior lawyers.

Myers, the most senior military officer of the most powerful country in the world, was one top official who did not understand the implications of what was being done.

Sands, who spent three hours with the former general, describes him as being "confused" about the decisions that were taken.

Myers did not realise that fundamental safeguards provided by the Geneva conventions and elsewhere were being abandoned by his own junior officers as well as political appointees in the administration, the author says.

He believed new techniques recommended by Haynes and authorised for use by the military at Guantánamo by Rumsfeld in December 2002 had been taken from the US army field manual.

Hopwever, none of the severe interrogation techniques came from the manual, and all breached established US military guidelines and rules.

The techniques included hooding, sensory deprivation and physical and mental abuse.

"As we worked through the list of techniques, Myers became increasingly hesitant and troubled," Sands writes. "Haynes and Rumsfeld had been able to run rings around him."

Myers and his closest advisers were cut out of the decision-making process, so he was not given suffficient opportunity to object to measures he now says he strongly disapproved of.

He did not know that Bush administration officials were changing the rules allowing interrogation techniques, including the use of dogs, amounting to torture.

"We never authorised torture, we just didn't, not what we would do," Myers said.

Sands comments: "[Myers] really had taken his eye off the ball ... he didn't ask too many questions, or inquire too deeply, and kept his distance from the decision-making process."

 Read the full story in Weekend magazine in the Guardian tomorrow and on theguardian.com