The programme heard from recent victims who told of severe beatings and sexual assault.
The claims come as the European Union pushes to let some banned diamonds from the country led by President Robert Mugabe back onto world markets.
The Zimbabwean government has not responded to the BBC’s findings.
In an internal document seen by the BBC, the EU said it was confident that two mines in the area now meet international standards and it wants diamonds from those areas to be immediately approved for export, which would partially lift a trade ban dating back to 2009.
The ban was imposed by the Kimberley Process (KP), the international organisation that polices diamonds, following reports of large-scale killings and abuse by Zimbabwe’s security forces in the Marange diamond fields.
‘Forty whips’
The main torture camp uncovered by the programme is known locally as “Diamond Base”. Witnesses said it is a remote collection of military tents, with an outdoor razor wire enclosure where the prisoners are kept.
It is near an area known as Zengeni in Marange, said to be one of the world’s most significant diamond fields. The camp is about one mile from the main Mbada mine that the EU wants to approve exports from.
The company that runs the mine is headed by a personal friend of President Mugabe. A second camp is located in nearby Muchena
“It is the place of torture where sometimes miners are unable to walk on account of the beatings,” a victim who was released from the main camp in February told the BBC.
All the released prisoners the BBC spoke to requested anonymity.
“They beat us 40 whips in the morning, 40 in the afternoon and 40 in the evening,” said the man, who still could not use one of his arms after the beatings and could barely walk.
“They used logs to beat me here, under my feet, as I lay on the ground. They also used stones to beat my ankles.”
They would handcuff the prisoner, they would unleash the dogs so that he can bite”
Former paramilitary police on torture techniques used
He and other former captives said men are held in the camp for several days at a time, before new prisoners come in.
Women are released more quickly, often after being raped, witnesses said.
“Even if someone dies there, the soldiers do not disclose, because they do not want it known,” an officer in Zimbabwe’s military told the BBC, again on condition of anonymity.
Witnesses said the camps have been operating for at least three years.
In Marange, the police and military recruit civilians to illegally dig for diamonds for them. Those workers are taken to the camps for punishment if they demand too large a share of the profits.
Civilians caught mining for themselves are also punished in the camps.