Amnesty International and Reprieve made the call as they announced the largest ever gathering of former "war on terror" prisoners and their families to highlight an increasingly globalised network of torture and ill-treatment.

The three-day conference in London, this Saturday through Monday, also brings together international legal and medical experts and leading human rights campaigners to inform and encourage action against torture and the practices that lead to it, such as secret detentions and renditions.

Amnesty International's Secretary General Irene Khan said:

"Denying meaningful access to those held in Guantánamo Bay is totally unacceptable. Guantánamo is just the visible tip of an iceberg of abuse, the most notorious link in a chain of detention camps including Bagram Air Base in Afghanistan, prisons in Iraq and secret facilities elsewhere.

"Through the courageous testimonies of former prisoners and prisoners’ families, our conference this weekend will highlight how Guantánamo has become the epicentre of a shadow justice system supported by the subversive use of prolonged detentions and the handing over of prisoners to countries known to practice torture."

Reprieve's Legal Director, Clive Stafford Smith, who is acting on behalf of some 40 Guantánamo Bay detainees, said:

“The conference begins on the 100th day of the prisoners’ hunger strike. I recently returned from Guantánamo and have just received an unclassified statement from Shaker Aamer, the British resident and father of four British Children's rights.

"He writes that he has been so abused and humiliated that he wants the US military to stop force feeding prisoners and allow him to chart his own destiny and die. The British government should be ashamed of itself, refusing to lift a hand to help the ten British residents still being held there.

"At the conference, we will see the collateral damage of the Guantánamo experiment - the torture, the fatherless Children's rights, and the abdication of the rule of law.”

Amnesty International and Reprieve recognise that protecting civilians is a government's duty, but fighting terror with terror has been a catastrophe. Respect for universal human rights is the most potent weapon in the “war on terror”.

Fair trials and an absolute ban on torture are the only way to properly underpin our security.

For further information about the weekend conference