"Manning has not been convicted of any offense, but military authorities appear to be using all available means to punish him while in detention," the human rights group said. "This undermines the United States' commitment to the principle of the presumption of innocence."
P.J. Crowley, the assistant secretary of state for public affairs, called the conditions "ridiculous, counterproductive and stupid."
After Crowley's comments to a group at the Massachusetts Institute of Technology became public, President Barack Obama told reporters he had been assured that Manning was being held under appropriate conditions that met basic standards.
In the ensuing flap, Crowley took "full responsibility" for his comments and resigned.
In court papers, Coombs said Manning was held in a cell directly in front of a guard post "to facilitate his constant monitoring."
When he was moved outside his cell, for a shower or for 20 minutes of "sunshine call" in a small concrete yard, the brig would be locked down and he would be shackled with metal hand and leg restraints and accompanied by at least two guards. He was not permitted to work.
Under prevention-of-injury status, Coomb said, Manning was issued a "suicide mattress" without pillow and a tear-proof "suicide blanket," which the lawyer said was coarse, did not retain heat and gave Manning rashes and carpet burns.
According to Coombs, a frustrated Manning told a brig official that if he wanted to harm himself, he could do so with the waistband of his underwear or his flip-flops. He was then forced to surrender all clothing at night and sleep naked.
Manning also was forced to stand naked at parade rest in view of several guards, Coombs said. Later, he was required to wear a "suicide smock," which Coombs described as heavy and restrictive, and said nearly choked Manning.
Manning had access to classified material as an intelligence analyst in Iraq. In pretrial motions and hearings, his lawyers have sought to portray him as a troubled young man who struggled with gender identity, was isolated from his fellow soldiers and should not have been given access to the classified materials.
Coombs also has suggested that the publication of the materials Manning allegedly released has not caused any harm to the United States.
Manning has become a hero to some anti-war activists, who say footage of the 2007 Apache helicopter attack that he allegedly released appears to show evidence of a war crime.
The attack in Baghdad left 12 dead, including a Reuters journalist and his driver. In the video, released by WikiLeaks under the title "Collateral Murder," the American helicopter crew can be heard laughing and referring to Iraqis as "dead bastards."
Manning's supporters say whoever released the footage is a hero who should be protected as a whistleblower.