The conference, which is organized by the human rights group Amnesty International and began on 18 November, is focused on allegations of prisoner abuse.
The detainees have gathered in London to share their experiences of the U.S. facility in Cuba and to seek more international attention to their grievances.
Airat Vahitov is a former Guantanamo detainee who is participating in the conference. He was previously jailed in Russia, Tajikistan, and Afghanistan.
Vahitov was born in Tatarstan and says he was captured by the U.S. troops from a Taliban jail in Afghanistan. He spent 18 months in Guantanamo and was released in February 2004.
Vahitov told RFE/RL his religious beliefs were mocked in the prison and he felt humiliated.
"Guantanamo Bay was not the first prison in my life, but there were such moments which I did not experience in other prisons," Vahitov said. "Namely, the kind of purposeful humiliation of human dignity, mocking religious feelings and the Koran. I haven't seen this in any other place."
He alleges that the behavior included acts deliberately meant to offend Muslim sensibilities.
"I saw imprints of American [soldiers'] shoes inside the Koran. People are being stripped and left in shorts only," Vahitov said. "And they walk for a month or more in these shorts, but it is not acceptable for a Muslim to pray being dressed in shorts."
Vahitov also called it annoying to have had to listen to the U.S. national anthem being played during Muslim payer time.
He said he would sue the U.S. government and hoped the conference, organized by Amnesty International, would attract international attention to the prison in Cuba.
Amnesty International researcher Sharon Critoph told RFE/RL that getting more attention focused on Guantanamo is the aim of the conference.
"Every day the situation becomes worse for the people in Guantanamo," Critoph said. "In this climate, it was about time we brought everybody to discuss the issues, to raise the profile of Guantanamo, but not just Guantanamo. This conference was about Guantanamo and beyond."
U.S. officials have denied charges that prisoners are treated inhumanely at the base. In early November, U.S. Defense Secretary Donald Rumsfeld denied prisoners were being abused.
"The president [George W. Bush] has required that the Department of Defense treat detainees with humane treatment," Rumsfeld said. "That has been the instruction that I've issued from the outset of this conflict and it is the standard to which the people at the Department of Defense are being held."
More than 500 prisoners of prisoners, suspected of belonging to Al-Qaeda or to Afghanistan's Taliban, are still being held at the U.S. military base at Guatanamo. Many have been held for nearly four years without charge. The United States declared the detainees illegal combatants not protected by the Geneva Conventions.
Meanwhile, a team of UN human rights experts on 18 November scrapped a scheduled visit to Guantanamo Bay, saying Washington was not allowing them free access to detainees there. The visit was planned after more than three years of discussions between U.S. and UN officials amid claims of human rights abuses at the camp. The United States said, however, that the invitation to visit the camp is still valid.