Ashvin Raman has made a groundbreaking documentary for German television which will be screened on Germany's ARD channel on 12 November.
His film includes exclusive footage of Guantanamo Bay, as well as interviews with released detainees and top American officials.
More than 600 foreign nationals have been detained without charge or access to lawyers and family members in the US naval base since November 2001.
The US has refused to recognise them as prisoners of war, or allow their status to be determined by a tribunal as required under the Geneva Conventions.
Raman said it was a scandal that two years after the US opened the camp, people were still being flown over there from Afghanistan.
He said: "Out of 660 people in Guantanamo Bay there are probably only five to 10 big names. The rest are just foot soldiers and ordinary people who were in the wrong place at the wrong time.
"Out of 660 people in Guantanamo Bay there are probably only five to 10 big names. The rest are just foot soldiers and ordinary people who were in the wrong place at the wrong time"
"The truth is that Afghans have a bad habit of informing on other Afghans. They sell people off by saying they are terrorists and many Afghan warlords have made a lot of money that way."
Raman, who presented a paper on Guantanamo to the European Parliament in September, said the camp was just "a showpiece for the American people".
"It is there so that Bush can tell them that he is doing something about terrorism. But you just can't keep people locked up for such a long time without charge or having access to lawyers."
Indian-born Raman said conditions inside the camp had not improved much since it opened.
"Things have only cosmetically improved. The fact is that if you are being held in solitary confinement in a cell that is five metres squared then that is not good. Don't forget, in the last few months 32 prisoners have tried to commit suicide."
He added: "The released prisoners that I spoke to just couldn't believe they had to spend a year of their lives there in the first place."
After the American war on Afghanistan in 2001, about 660 people from 42 countries were sent to Guantanamo Bay for interrogation.
The detainees were taken to a place outside US territory to minimise the application of legal constraints that might otherwise apply.
The Guantanamo prisoners are in
The Americans say the Guantanamo detainees are being treated humanely and receive good food, excellent medical care, and the opportunity to worship.
However, the US considers them as "enemy combatants", which means they are outside the normal legal framework and can be held indefinitely without trial or access to lawyers.
Washington says it cannot treat the detainees as normal criminals because of their alleged links to Usama bin Ladin's al-Qaida network.
Neither are they regarded as prisoners of war under the Geneva conventions, because they were not members of the regular Afghan armed forces.
The Pentagon has announced that six Guantanamo prisoners are likely to be tried by military tribunals.
The defendants may face prosecution on a number of charges, including violations of the laws of war.
Depending on the particular charges, the death penalty may come into force.