Former US president George W. Bush is expected to attend an economic summit in Surrey in Canada's westernmost British Columbia province on October 20. – File Photo by AP

Bush is expected to attend an economic summit in Surrey in Canada's westernmost British Columbia province on October 20.

London-based Amnesty made a case for Bush's legal responsibility for a series of human rights violations in a memorandum submitted last month to Canadian authorities but only now released to the media.

“Canada is required by its international obligations to arrest and prosecute former president Bush given his responsibility for crimes under international law including torture,” Amnesty's Susan Lee said in a statement.

“As the US authorities have, so far, failed to bring former president Bush to justice, the international community must step in. A failure by Canada to take action during his visit would violate the UN Convention against Torture and demonstrate contempt for fundamental human rights.” Lee said.

Amnesty, backed by the International Civil Liberties Monitoring Group, says Bush authorized the use of “enhanced interrogation techniques” and “waterboarding” on detainees held in secret by the Central Intelligence Agency (CIA) between 2002 and 2009.

The detention program included “torture and other cruel, inhuman and degrading treatment (such as being forced to stay for hours in painful positions and sleep deprivation), and enforced disappearances,” it alleged.

Amnesty's memorandum cites several cases of alleged torture of individuals detained at the Guantanamo Bay naval facility, in Afghanistan and in Iraq, by the US military.

They include that of Zayn al Abidin Muhammed Husayn (known as Abu Zubaydah) and 9/11 mastermind Khalid Sheikh Mohammed, both arrested in Pakistan, and subjected to at least 266 applications of waterboarding between them from 2002 to 2003, according to the CIA inspector general, cited by Amnesty.