Afghan prisoners taking part in a US study have claimed they were abused at a secret jail inside the main American military base in Afghanistan.

Former inmates told the Open Society Institute they were subjected to sleep deprivation, extended periods of isolation and a lack of food and blankets. Some of the claimed abuses date from this year, despite President Barack Obama's pledge to overhaul prison practices.

Former CIA officer Philip Giraldi said this does not surprise him because “the Obama administration is many respects worse than the Bush administration.”

“When Obama was running for president he talked a very good story about what he is going to do, but he actually has done very little of that,” Giraldi told RT. “We see the escalation of the war in Afghanistan, we see the secret prisons continuing, the government using what they call the ‘security privilege’ to keep it from being challenged in court on many of these prison-related issues.”