America's most controversial writer Gore Vidal has launched the most scathing attack to date on George W Bush's Presidency, calling for an investigation into the events of 9/11 to discover whether the Bush administration deliberately chose not to act on warnings of Al-Qaeda's plans.

Vidal's highly controversial 7000 word polemic titled 'The Enemy Within' - published in the print edition of The Observer today - argues that what he calls a 'Bush junta' used the terrorist attacks as a pretext to enact a pre-existing agenda to invade Afghanistan and crack down on civil liberties at home.

Vidal writes: 'We still don't know by whom we were struck that infamous Tuesday, or for what true purpose. But it is fairly plain to many civil libertarians that 9/11 put paid not only to much of our fragile Bill of Rights but also to our once-envied system of government which had taken a mortal blow the previous year when the Supreme Court did a little dance in 5/4 time and replaced a popularly elected President with the oil and gas Bush-Cheney junta.'

Vidal argues that the real motive for the Afghanistan war was to control the gateway to Eurasia and Central Asia's energy riches. He quotes extensively from a 1997 analysis of the region by Zgibniew Brzezinski, formerly national security adviser to President Carter, in support of this theory. But, Vidal argues, US administrations, both Democrat and Republican, were aware that the American public would resist any war in Afghanistan without a truly massive and widely perceived external threat.

Osama was chosen on aesthetic grounds to be the frightening logo for our long-contemplated invasion and conquest of Afghanistan ... [because] the administration is convinced that Americans are so simple-minded that they can deal with no scenario more complex than the venerable, lone, crazed killer (this time with zombie helpers) who does evil just for the fun of it 'cause he hates us because we're rich 'n free 'n he's not.' Vidal also attacks the American media's failure to discuss 11 September and its consequences: 'Apparently, "conspiracy stuff" is now shorthand for unspeakable truth.'...