A Guantanamo Bay inmate's prison memoir has revealed disturbing allegations of 'torture', including being forced to have sex with female American soldiers.

Mohamedou Ould Slahi, an alleged al-Qaeda associate, reveals in his 466-page memoir titled 'Guantanamo Diary,' that female interrogators told him: "Today, we're gonna teach you about great American sex."

In his memoir, which was published this week following a six-year legal battle, Slahi claims two women "took off their blouses, and started to talk all kind of dirty stuff you can imagine, which I minded less. What hurt me most was them forcing me to take part in a sexual threesome in the most degrading manner.

"I had a mask over my mouth and my nose, plus the bag covering my head and my face, not to mention the tied belt around my stomach. So breathing was impossible. I kept [saying] 'Mr, Sir, I cannot breath... Mr, Sir... Please'. It seemed like my pleas for help got lost in a vast desert."

Slahi was charged with having ties with al-Qaeda, but interrogators did not have any evidence of his involvement in a terrorist act.

His connections with al-Qaeda include an alleged acquaintance with 9/11 conspirator Ramzi bin al-Shibh while his cousin was bin Laden's advisor.

Slahi has been held at the at Guantanamo Bay for 13 years.

In 2010, a US district court judge James Robertson ordered Slahi to be released due to lack of lack of evidence over his direct involvement with al-Qaeda, yet he remains in prison, reported The Huffington Post.

Slahi's 'Guantanamo Diary' was launched in London on Tuesday (20 January) by his lawyer Nancy Hollander, brother Yahdih Ould Slahi and human rights activist Larry Siems, the book's editor.